Why not just use durations directly for the type?
Additionally, consider using a struct to contain these.

type ABCIDelays struct {
PrepareProposal
...
}

Does TOML support durations or are you suggesting I just convert it after parsing the toml file?

Our toml parser supports parsing duration strings into go durations.

see

Let me change it up then

testnetCombinations defined in line 15 was adding the possibility to test "builtin" and "out of process".
This also modified nodeABCIProtocols in line 29 (BTW, looks like we are not testing GRPC as it is now?).
Do we want to backport this change in structure of the variables controlling the test combinations?

gRPC seems to have been purposefully disabled due to #5439. It's hard to judge whether this is still an issue

We can look to port more of the e2e functionality later. I kind of want to pick off important chunks first

Agreed. Anyway remember that this effort is not in the critical path (i.e., it's not blocking the creation of branch v0.37.x). IOW, it can proceed along with the release QA process