I’ve been using - an SW-Motech tank bag for a while so thought I’d add some comments to this thread. I chose the SW-Motech EVO 2 Daypack combined with a Type 140 EVO 2 tank ring (TRT.00.640.14000.B).
Based on information from this thread, I decided the Daypack would be a good choice. It’s much smaller than Engage Sport tank bags I’ve owned previously, but the larger bags don’t seem such a good fit on the H2 SX SE. Regular capacity is 5 litres, which is OK for a couple of bottles of water, snacks and bits and pieces you might need during a day ride (it is called Daypack

). Capacity can be increased by undoing a zip around the base of the bag and expanding it.
The Daypack fits nicely. It doesn’t block the view of my GPS and there’s no interference while riding. It’s possible that in the expanded 9 litre form my chest or arms could touch the bag, but I haven’t tried that configuration. In either format you won’t be able to crouch below the screen chin-on-tank style, but I haven’t felt a need to do that on this bike and I do have a low screen.
I went for the optional electric adapter. At first, I thought about rigging my own power supply. The electric option seems expensive for a few wires and a relay but it’s worth it for the convenience of fitting or removing the bag without plugging/unplugging electrical connections. The electric kit includes a relay that cuts power when the bag is removed so you don’t have live terminals on the exposed tank ring.