I use RedditList to find subreddits to post on. The tool itself is easy to use (and free) and the only request I have is to update subreddits more frequently and add subreddits outside of the top 5,000. With how large Reddit is now even 10,000 would still have very large subreddits missing.
Started using BoostUpvotes after joining Reddit last year for my content business and I've since recommended it to every OF creator I know. I now use them on most posts and consistently hit the top of the largest subreddits.
Support has been extremely helpful and went above and beyond for a post I needed custom services on.
I'm sure there are other services out there but Protonmail being widely adopted and having years of operation behind them made me choose them. I've found they're much less heavy on the marketing than other services once you've signed up and have used the VPN services as well without issue. Overall highly recommended.