I understand that the Bolt is too small for you. However, as far as I understand, the operating system for the Bolt and Roam is the same.
This means that you can "test" out things like the Strava turn by turn on your bolt. If it works on the Bolt it will work on the Roam.
The Roam will give you a slightly bigger display, some colour and the ability to re-route or navigate on the fly.
As long as you have a data/wifi signal you can create routes on the fly and send them to your Bolt either through the Wahoo app or another planner.
(It's also possible offline but that requires a cable).
I understand the head spinning
Sometimes it's helpful to make a list of features, show which models are compatible and then prioritise according to your needs and preferences.
Like I say, "Navigation" varies from unit to unit, unlike a car sat-nav.
Personally, turn by turn has never been important to me, nor rerouting. I have been able to use the basic Wahoo maps to head in the right direction.
I have no interest in any monitoring.
I got a good deal on a Roam due to a failing Elemnt battery.
I'm not sure if I'd consider a full price Roam to be good value for money.
(The Elemnt is the same as the Bolt, only bigger. It may be an option for you if you can find one. They are discontinued).