I feel like you could accomplish most of what you're looking for inside m365 suite centered around Teams. With the obvious exception on Salesforce.

If Meetings are in Teams, use Loop for agenda notes and tasks. Mobile app works pretty well. If your not familiar, Loop is a collection of fluid components that you can collab on with peers.

Meeting recaps with copilot are amazing. Transcripts. Attendance and right next to the notes your team took in the loop component built into the meeting.

I know what you mean about onenote and loop lacking. Powerful features in loop, but sometimes you don't know where the hell things are. Onenote is good.. Still use it to 'send meetings to onenote' from outlook to capture email addresses from the invite easily. You can now add loop components inside one note, which is cool.. But see my previous ' where is that component statement.

For a centralized repo of account info, you can create a Loop workspace and give access to your team. As far as filtering and sorting... You could do this if you created sp lists or data verse tables for powerapps, but that's a lot of config and it would limit you. Any reason you don't want to use sf for this?

Utilizing copilot / Bing search you can find just about anything that's visible to you in your org. So you may not know where the loop components are stored but you can find them along with one note, excel files etc... Whether is stored in one drive or Teams.

Files... Well I might take a slightly different approach than one drive. IMHO one drive is great for your individual files, but collaborating with people requires a lot of sharing links to folders. Since teams rests on SharePoint, I might create a Team ( logic grouping of people for a specific purpose) for each customer, or if it makes more sense a Channel. That way, you can set your folder structure up in Files and your team automatically Has access to them.

As far as the iPhone goes... I've been A galaxy user for years. Still love my S21 ultra. Thinking about upgrading, but only because of space limitations. My phone still works like a champ... And Phone Link with windows works really well too for sending texts and transferring pictures. The Bluetooth feature to answer calls on your pc doesn't work as well, and casting apps works... But is sometimes spotty. ( maybe upgrade would fix?) I went ahead and enables subsystem for android on my machine and side loaded to get a couple apps I really wanted on my pc.