I have apples on this account but I've decided to create a new account and make that one my main one and use this one occasionally. Is it considered transferring apples between accounts if I use this account to pay for something I will use on my other account? For example, art or ocs that require apples, and I send the artist the apples through this account.

Yes. Transferring anything at all, be it wolves, apples, mushrooms, decor, gear, or anything else, or using an account to otherwise benefit from, is considered against the rules. If you are found benefitting from another household account linked to you, you may be suspended or banned.

On a separate note, minimodding is not allowed. Thanks.