The one lack on Pop Peeper is a real search function. 
I just added my thoughts about it here on this thread.

Is there a way to Search emails with a keyword?
https://www.esumsoft.com/Forums/viewtopic.php?f=3&t=6173

ADDED: Version 5 is being worked on!

Pop Peeper is working superbly.

Right now I have about five Gmail accounts hooked up, including one from Gsuite (private domain, biz). Today's mail is on top, and I can work with an individual account, or all the accounts combined, nicely color-coded. 

Impressive. 
Are any of the others good in that way?

Two specialty things for GSuite are
1: Kiwi extension have to check what it actually does, I keep a tab in Windows that is only for that GSuite biz account.
2: Google - Drive File Stream maps the Google Drive to a Windows letter like G:

Now they just say:

"Down for Maintenance"