It really depends on how well you do your record keeping and how much separation you want.
I find it is convenient to have Paypal, direct deposits and checks from shops all go into the account that also receives my SS direct deposit. That yields really good tracking of income. Other checks I receive go into a different account as they are usually rebates, reimbursements not associated with shops (picking up groceries for a neighbor and she writes me a check), birthday checks and other miscellaneous checks.
As for expenses, I pay most everything out of the account that receives my income. There are a few expenses (birthday checks, donations, etc.) that I pay out of my "other" account.
When I first started shopping I established a 'shop kitty' that I could feed reimbursements into so that I would have some limits on how much I would outlay at any given time because usually it is 30 to 60 days before you are reimbursed. My 'kitty' has evolved into a savings account that is 2X what my maximum outlay for shops per month should be. When I set up my bills to be paid I will transfer money back and forth to the 'kitty' as needed. Once all the bills are set up to pay, anything left beyond the minimum deposit to keep the account free gets transferred over to my brokerage account for investment.