There are many factors to consider, not only the proxy part. Anyway, let's say you have good e-mails, good anti-detect browser and you only need the best 4G/LTE mobile proxy (I will not talking about how to warm the accounts, which is also a very important part - you can find some effective strategies on the forum): I offer 3-minutes proxy rotation interval (minimum), so you will have 20 individual proxies/1h. In theory, you can create 20 accounts per 1h (or 480/day/ 4G dongle), but after that, there is no guarantee Reddit will not ban them.
The best I can recommend is to test one and see if it fits or not with your project.
Cheers!
M