You may have already tried, but I'm currently running a cassette with a 30 tooth large cog with a standard eTap rear derailleur. Just had to adjust the B-screw a bit, and I could take it even further in so could maybe squeeze a 32, although I didn't attempt that yet.

I have not tried that yet. Another option I was considering is the wolf tooth roadlink, any experience with this?

Haven't tried that since this worked for the purpose I needed, but I've had good experiences with other Wolftooth products, so can't see this being any different.