I use all accounts from Mail on my iPhone; all except my employer's account via Mail.app on my MBP; and my employer's GMail via the GMail web on my work laptop.
I use +-suffixes extensively for signups, etc, so I can blackhole spam when my address gets leaked ...
If you'd switch your phone, does the need to sync the display names and signatures bother you? That, and the need to log in manually to all these 6 addresses?
When I switch to my phone, also using the iOS Mail application, it's all synced up.
I seldom need to log in: the Mail apps use my keychain to sign me in to all the accounts transparently.
I have at least one signature for each account, and several for some. When sending a new email, I select the correct source address (two taps/clicks), and signature (another two clicks) if the default isn't correct.
Replies set the account automatically, so I just need to choose the signature there.
Same with a new laptop (4 times in about 15 years) -- I just transfer all the settings over, and I haven't ever needed to redo anything.