Hi @a1tb1t@lemmy.one~ I'm the admin of lemmy.one (I know you also messaged me on Reddit). The specs for this server are roughly double the specs of lemmy.ml's server, except we're ~10x smaller than lemmy.ml at the moment, so we have lots of room for growth. I run mstdn.party which is one of the top 40 largest Mastodon servers according to the-federation.info, and I'm prepared to scale this community as well. If you want your community hosted on this instance, I'm happy to get that set up for you, we can talk further on Reddit.
If you're considering running your own Lemmy server instead, it is not particularly resource-intensive, I would imagine you could host up to ~1000 monthly active users on a server that costs no more than $30/month. I'm happy to invite you to some Lemmy admin communities who can provide assistance as well if you're interested in going that route.
I prefer the browser to apps personally, this is actually one of the main reasons I like Lemmy over Reddit and it's unusable mobile view. You'll find plenty of mobile app users here too and it sounds like it works fine, I'll just caution that some (all?) of them sound like they're feature-incomplete, so if you ever think something is missing from Lemmy, double-check on the website first, because it might just not be added to the app yet.