I don't know if OP's intention is to do an investigation to see what the trend is for players who play only with BTC and how they bet, but in terms of platforms there are many and the best ones are here in the forum, the sites and platforms are many, in fact several reviewers are dedicated to this, but what I can say is that currently the multiple varieties of platforms that exist accept BTC and some have very low withdrawal fees, others high, I would go for the known platforms for stake my BTC, which I would do very responsibly.
That's better if he will investigate first before he gamble so that the chance of being scammed will get lessen because not all users here can recommend a legit casino but there are also some that shills a scam casino. Crypto gamblers don't use btc alone but they also use altcoin. Not only that altcoins has some certain benefits but because btc is too valuable for them to gamble and lose.
Yes, we have reviewers here in bitcointalk, they review gambling sites, some of the trusted ones are
gamblingbro and
btcgosu. He can check that out for a more precise review. Each site are not the same, thats why some has a high fee and others have less but what's more important is that the site is trusted.