I'm not sure there are any ergonomic Topre keyboards.
So it really comes down to whether you want an ergo layout or a conventional layout.
If conventional, you can still choose Topre or MX. Or Hall Effect. Or Alps. Or buckling springs.
If you go ergo, you'll be much more limited, pretty much MX (although there are many, many MX-compatible switches to choose from).
If you've tried an ergo keyboard before and got on really well with it, that would seem to be a reason to stick with the layout.
If you're planning on swapping switches and/or keycaps around a bit, a more conventional MX-based layout would be easier, although support for ergo/ortholinear keysets are improving.