First, are ya'll set on the names "Fredrich" and "Emrys"? If so, I'll get your names switched over.
Second, Fredrich/P1: it sounds to me that you are leaning towards a social/political character.
If you go Tremere, the pros/cons as I see them are:
-You will have a superior. So expect to get some orders at some point
-You may be able to leverage the Tremere's network on occasion.
-Some players really like the whole "work your way up the ranks" aspect.
Pros/Cons of the Bonisagus route as I see them:
-You have more control over your own agenda
-You do not have as much House support for your agenda
My personal choice would be the Bonisagus route. But that's me. I've always been more of a Tytalus guy than a Tremere guy.
The Grogs. I'd like you each to come up with two grogs a piece for a total of four.
First, I'd like for you to run each other's shield grogs. You can assume these grogs were issued to your magi from Fengheld's troops and that grog is now the magi's to control. Consider it a perk for being part of Fengheld.
Second, I'd like two other grogs and that's a bit up to you two to decide. I'd recommend one more soldier and maybe one servant. Some additional muscle and someone who can act as your agent in dealing with the mundane folks. But that's a suggestion. I wouldn't try designing a craftsman or anything like that. Leave that for post-game/covenant building.
Questions?