I ran this arrangement for a year or three, until dicky knees forced me back to gears. If your rides involve a long flattish section to get to/from the hills (my rides generally feature 8-10km of canal towpath at each end) then it’s a good solution.
Changing ratios is a slight faff, but not much more than refitting a thrown chain.
Chain line is easy; just use two cassette spacers between the sprockets to match the spacing of the chainrings. Ratios are also easy. I ran unfashionably large chain rings, and used ratios of 44:18 and 40:22. But as long as the total tooth count is the same for each ratio, the change in chain tension is small enough for it to function in both ratios without adjustment – there’ll be slightly more slack in the lower ratio, but not enough to cause any trouble. Your suggested ratios, being only 2 teeth different in ring size, should work even better. Although I’d question whether there’s any point in having gears so close together. Depends on your riding – the above ratios worked for me in and around the South Wales valleys and Brecon Beacons.
Don’t consider the Sturmey two speed. Kickback gear change is a PITA on a road bike, and would be a nightmare off road (I had one on my Moulton, and replaced it with an Sram Automatix). They also have (literally!) zero sealing.