I love low alcohol beers. Here's a few styles I've played around with:
1) Ordinary Bitter/Golden Ale: CAMRA cites OB as 3.4% to 3.9% abv but I've seen some as low as 3%. A basic recipe would be 90% British Pale Ale Base Malt (Marris Otter/Golden Promise), 6% Medium/Dark UK Crystal Malt, 4% Wheat Malt. Hopping is flexible, it seems the English differ from the Germans in incorporating some American style hopping (sometimes US varieties and heavy late/dry hopping). The combo of flavorful British Ale yeast (could even try open fermenting a top cropper), UK malts, and a decent hop character can make the beers pretty flavorful despite such a low gravity. It may seem unusual but I actually did a Hockhurz mash on my last Golden Ale - the long rest at 160f seems to help with body and foam. Single infusion I go on the higher end, like 154f. Golden Ales are all or mostly pale ale malt with more aggressive hopping. I have a 3.9% one on tap now that was Golden Promise, EKG, Wyeast 1469 (T. Taylor yeast). Think the yeast, hops, and low final pH leave it with a citrusy sort of flavor.
2) Berlinner Weisse: I only helped brew one once with a buddy so by no means an expert. But he kettle soured a berlinner that came in around 3% and it was solid.
3) Czech Lagers: BJCP style guidelines seem to be a off on ABV but this site gives a nice overview (http://www.europeanbeerguide.net/czecintr.htm
). The Czechs brew 8-10 plato (3-4%) lagers in pale, amber, and dark varieties. This slideshow goes in depth (https://www.homebrewersassociation.org/attachments/presentations/pdf/2015/2015%20AHA%20Czech%20Lagers%20-%20History,%20Brewing,%20Judging.pdf
4) Trappist Singles/Pattersbier: Something I want to look more into. Only one I tried was basically a pils with Trappist yeast. I have a lot to learn with these.
5) Irish Dry Stout, as you mentioned: I have one fermenting now - 70% Base Malt ( I split TF Golden Promise with Munton's Mild Ale Malt), 20% Flaked Barley, 10% Munton's Roasted Barley. Used the 1469 I've been open fermenting/top cropping, and bittered with a hop shot to 35ibus. Guinness finishes with a low pH (3.8 or 3.9 IIRC?) and has a bit of an acidic twang but a lot of folk like the pH higher on stouts and mash as around 5.5. I added the Roasted Barley late once (after mashing Pale Malts at 5.4) and my final pH was 3.85 with the acidity being a major flavor component.