And expensive...[emoji35]Both require special frames. Shaft drive is les efficient and heavy.
Also prevents use of fully enclosed Chainglider chain protection.Derailleur type tensioner looks a bodge to me but probably easiest way for chain/belt wheel removal.
You are a star sirWith IGH's you have to decide between front hub or cd. A cd will cover most aspects of riding even hills (10%) but with hub you will need to select one with an rpm that suits your needs.
A 20t sprocket for instance combined with the nexus or alfine 8 will give you a gearing of 38,31,27,24,20,16,14,12 in a cassette, as can be seen not very even leaps in gearing.
Shimano recommend 1.9.1 gearing ratio but have read other forums where user have gone above.
Recommended chain wheels and sprocket for close to 1.9.1 ratio I believe are 36/16, 38/18, 42-44/20 & 46/22.
46/20 gives a higher 2.1.1 ratio.
It might be your best bet to test with your own bike first, its an absolute minefield out there in terms of market availability.I have been looking at hybrids with Alfine 8 for a conversion with a bbs01, Ridgeback flight04 looks very nice but has eccentric bb. A closer look at the bb suggests a bbs will fit with the positioning of the ebb as it sits.
The other option is to try and convert my ht mtb with one to try as a off roader as mtb forums suggest they work quite well and seem to cope with up to 750w of power.