I've been using Office 365 Business Standard. Works quite well, works with all my devices (Windows natively, web with a very good web interface and iOS with the Outlook app and with Exchange syncing). Works nicely with a standard Microsoft account and can switch between them depending on what I need (e.g. Xbox/Rewards on personal account). Had to migrate stuff manually (using Google Takeout) to a 'normal' Google account which was pain - especially as they let you go from personal to Gsuite in one click - but once it's done it's done - thankfully Office 365 keeps the subscription & standard Microsoft account separate. Lost a YouTube account in the transfer but had to suck it up.

Can get a subscription for around £90 a year, usually with cashback through various retailers via the likes of Topcashback/Quidco (renewed last time with the BT online store and got cashback through TCB).

Spam filtering is second to none, nothing seems to get through it and doesn't have many false-positives either.

I've replaced it with purelymail.com (not affiliated) - and I'm happy with that. Been with the service for about 4 months now. Yes, there is occasional spam, but fine with that.

They offer calendar as well, works fine but I am not using it. Running my own self-hosted instance of NextCloud and using that for cal and contacts.

I do not use any online/web office suite.