First, there are no "best way to study". Only pros and cons.
Second, up to you. Both are viable. IF you do additionnal things and don't follow renshuu basic schedules (because those are oriented towards the JLPT, which is also oriented towards reading).
Native Japaneses (as well as polyglot most of the time and some online learners) learn without kanji first. Rather than learning words, grammar, or kanji, they learn patterns first. And later, they learn grammar, which allow them to understand how they speak, and kanji, which allow them to differentiate written words. That last part is important because people often think spoken japanese and written japanese are the same but that's not the case... at all. There are even expressions which are often used by native for that: 話し言葉(はなしことば) and 書き言葉(かきことば). And the way they learn Japanese reflect that too.
For example, あし is often translated by foot or leg. Well, in spoken japanese and for kids, it means neither. It's closer to limb. Basically, it was a 大和言葉(やまとことば), a word of japanese origin and when kanji arrived, it got differenciated (with 足 and 脚). But in spoken japanese, it didn't change. Furthermore, 足 (foot) is learn around 7 years old but 脚 (leg) is not learn until 13 years old. So during that period, あし is still just limb.
It's just one example but there are a lot of other case like that. As well as other things that happened when you don't focus on kanji first and learn in a native or polyglot way. One of the most important factor is: it force you to rely on context.
Instead of learning 撮る for example, you need to learn things like しゃしんをとる (take a picture) to differentiate the different とる (取る、#撮る、#捕る, 採る) without kanji. Basically, compared to most foreign learner, japanese kids have an easier time because they don't differentiate words like that. And later when they finally learn kanji, they just "realized" that they were different words. And they do take their time compared to foreigner: 80 kanji in the first year and "only" a 1000 kanji after 6 years. Most foreign learner rush the kanji instead and get confused early on by those homophones. Like it slow them down. But once they are past a certain threshold, it makes learning new words easier. But only after that threshold.
And it's the same for conjugation. Context and pattern help you to distinguish and remember those kind of things.
Basically, natives japanese and polyglot tend to learn only a small amount of things and "use" that small amount of things to learn basic pattern (which is different from grammar) and develop their ability to deduce meaning from context rather than words directly.
There are a lot of others things that I'm not talking about but to sum up, yeah, it's possible and viable to not learn kanji in the beginning. Especially if your goal is to progress evenly on both your reading and listening ability.
But wether you can do to renshuu with renshuu is another problem. Renshuu basic schedules are oriented towards reading and the JLPT. So, if you really want to use those schedules, I wouldn't recommend you to turn off the kanji. Because there are almost necessary.
Otherwise, just study the kaishi 1.5K words AND sentence schedules. And go practice with natives as soon as you learn a new set of sentences. There are a lot natives online to practice with for free and they also can't to practice their english once you're struggle to produce to some sentences. Later, just do the same for beginners.
Once you're done with the first thousand words, start to learn kanji and grammar. It will be a lot more easier to study.
If you can do that, it will be viable. Otherwise, it won't. Because you will lack that input that natives naturally have and which allow them to learn that way. Also, past 1000 or 2000 words, not learning kanji will definitly start to hinder you.
But until then? Well, that's just how natives learn. And polyglot. And polyglot usually learn way faster than most learners.
At the same time, it's also a matter of personality. If you can go to language exchange community (on discord or VRChat for example) to meet and talk to natives, it will work. But not everyone can do that.
Honnestly, both strategy/way to learn are the same for me. People that ignore kanji and go straight to interact with natives usually get good speaking and listening early on (but are really bad at reading/writing... As well as grammar). People that don't ignore kanji usually get good at reading/writing sooner (but are really bad at listening/listening even after a few years). After a few years, when they finally encounter a real wall or plateau, they finally start to work on their weaknesses.
Btw, I'm the type that want to get good at both at the same time. The current result is that I'm bad at both compared to both extreme. But I'm also better than both when it comes to their respective weaknesses. And I'm fine with that. I sometimes regret that I did not study in more "polyglot way" because I have more fun conversation with some japanese friend. I don't regret it when I saw those people struggle because they don't enought kanji. I sometimes not having rushed the kanji (I'm around 1200 after 4 years). I don't regret it when I was those people struggle with basic conversation while I can enjoy casual japanese full of slang. At the same time, don't talk to me about daily life things or small talk. Don't ask to read too except for the things I like or read (like japanese grammar for native). I will start to read once I reach Japanese high school level because it's either too boring or inefficient imo (but some people do it and there are to do it if they are stubborn enough).
Anyway, whatever you choose, it's the same in the end. And most people end up correcting their weaknesses around 5 years in. So up to you.
Oh and another fun fact. Renshuu recently uptated the kanji database with a native online dictionary (called jitenon). Along with dictionary came the wonderful JP definition! Most of the time... It's full of hiragana words. To define kanji, Japaneses use... hiragana words. Ironically.
TLDR: Natives and polyglot don't focus on kanji first. They develop a foundation by speaking and listening while remembering pattern and understanding meaning through context. After that they focus on kanji and grammar. It's not "better", just a different way to study with pros and cons. But if you rely only on renshuu and use renshuu basic schedules, it won't work because you lacking the most important part: Native input and conversation practice (which is easily doable with internet nowadays). So up to you, but if you want do it, do it properly. Otherwise, follow the advises of the community. Because they are good at studying the way they do and at using renshuu.
