As far as I know, the only difference between the Express 4K 3940 and the Express 4K+ 3941 is that the 3940 is supplied with the Simple IR remote and the 3941 is supplied with the wifi Voice Remote. The Roku itself is identical and should work with both IR and wifi remotes.
I think the info listed on the Roku comparison page just refers to which remote is supplied with each model, not compatibility information of which remotes will work with each model.
Flagging this to bring it to the attention of Roku employees RokuDanny-R, RokuKariza-D, & RokuMary-F for confirmation of the above.
Meanwhile,renojim's suggestion of purchasing locally from a retailer with an accommodating return policy is a good one.