Best practice guidance wanted for a multiplayer turnbased word game played in realtime

Hello!
Best practice guidance wanted for a mobile word game that is turnbased but played in realtime (each turn is less than a minute and each player sees the other players letter selections in realtime):

1. What technique to use for shared gameobjects (letters), currently they are instantiated as room objects.
2. How to manage the situaton where any player temporarily (perhaps for just a minute or so) leaves the game fo something, i.e. check sms, and thereafter would lika to continue tha game.
3. Currently RPCs are being used to communicate over the network but is still really the preffered way in this case?

I am happy for any ideas on these matters. Good tutorials, Youtube videos, Lessons on Udemy or similar. If there is anyone having the knowledge and may be willing to spend some time to look at the code (maybe over teams-meeting) that would be really awesome.

Gameplay:
- Letters are being instatiated on a shared game board
- Each player (once it is their turn) may click on them to crate words which gives scores
- Each turn lasts less than a minute
- During each turn the player which is not in turn sees tha other players selections in realtime
- Three is also an element of each player have cards to be played which effects gameplay and needs to be visisble in realtime for both players

Regards
Mikael