Newb question about proxies

I've read/searched a lot of threads on proxies, but I still have a really basic noobie question. I know the consensus is that only 3-5 accounts should be used per proxy. And for ultimate safety, only use one proxy per account.

Just to clarify, this is per account and not per IG service. For example, if I'm using multiple IG services per account (like FL and Onlypult) then I would want to use the same proxy in each service per account. I would never use different proxies for the same account in two separate IG services. Thanks in advance and apologies if this is a stupid question. Just want to make sure I'm doing everything right.

Always use that proxy which is associated with your Account , what so ever service you are using .

Well what if my account is not associated with any proxies? I use IG on iPhone without proxies, but for FL and Onlypult I of course use them. And so I need to use only one proxy for both FL and Onlypult?