I would appreciate your advice on this DIY design

I'm remodeling a second floor master bath (13'x14')and would appreciate a confirmation that I'm on the right path (or not). The existing stack is 3" PVC, there are three existing vents (2 are 1 1/2", 1 is 2") vented through roof, walls are 2x6, floor joist are doubled 2x10. Location: Fort Collins, CO.
Diagrams are attached.

Several specific concerns:

1. Is the design over-engineered, especially vents and clean outs?
2. Can I tie into a horizontal branch with a wye laid flat (without rolling)?
3. On diagram B, with is the drain for two sinks on an outside 2x6 wall, there are 2" holes already drilled in each of the studs 36" from the floor from the previous install. The vanity will be set at standard height. Can I run the vent through the existing holes or do I need to drill new holes for the horizontal vent pipe? Another way of asking this might be "when code says the horizontal vent must be at least 6" higher than the flood height of the fixture, is that the flood height of the drain in the sink or the top of the sink?
4. On diagram A, is it legit to run a 2" vent off the top of the 3" San Tee?

quote; 3. On diagram B, with is the drain for two sinks on an outside 2x6 wall, there are 2" holes already drilled in each of the studs 36" from the floor from the previous install. The vanity will be set at standard height. Can I run the vent through the existing holes or do I need to drill new holes for the horizontal vent pipe? Another way of asking this might be "when code says the horizontal vent must be at least 6" higher than the flood height of the fixture, is that the flood height of the drain in the sink or the top of the sink?

It is the top of the sink, but You missed the part that says "OR 42" above the floor whichever is HIGHEST", so you cannot use those holes.
Where are the "diagrams"?

The diagrams are uploaded now. Had issues with file size...