Di2 is no brainer, for you. IN stead of trying to decipher what you have and what you'd need (I think because it's 10pm in Belgium, and I might have had a few beers with the club after today's 180km road ride to the sea coast)....
Here's what my '21 Diverge is rocking, in Di2 trim;
Levers: GRX ST-RX815-R/L
FD: na
RD: RD-RX817
BB: SRAM DUB (BSA)
Crank: Quarq DUB Carbon with DZero Spider, 46t chainring (42t swaps in on hilly courses)
Cassette: SRAM XG1175 (10-42)
Front brake: BR-M8120 (4-pot post mount, on a flat mount to post mount adapter...much better modulation, and tons of stopping power, maybe more than I need)
Rear brake: BR-RX810-R (flat mount, rear)
As you can see, really you just need the levers and correct RD. I chose to run the SRAM cassette on an XDR driver (with spacer to make the MTB cassette compatible) so preserve the top end while getting the low end I wanted for loose gravel climbs. The key thing is that the move to Di2 for you seems pretty straightforward, really just levers, brakes, and a RD. You don't have to run a SRAM cassette, I just chose it since my wheels had the XDR free hub included when I bought them, but if it hadn't I'd have stuck with Shimano and suffered some top end loss, though in reality, I'm not sure how much it would have been in practice.
Go for it. Di2 is bombproof. Once properly set up, you can ride it forever without messing with it beyond chain maintenance and changing cassettes, and of course charging it up!