Personally, i wouldn´t use the resolution as the determining factor, i would check, if i can build detailed enough tilemaps or scenes with the tiles available (for lenght and width), while making sure, that the tiles themselfes are not too low res, or have a fitting style and charme.
What i mean is, can you design all the scenes with 26x15 tiles? (if i count that correct).
Will the rooms have enough interesting stuff? Because usually the world scrolls left right up and down, if the artist can´t fit everything into one scene, but you decided to basically have no scrolling, each room is one level, so to speak. of course, you always can use multiple screens for bigger structures or buildings.
One game i know (an ancient DOS game), that uses the same way of displaying the world, is built with 40x30 tiles (4:3 resolution for the number of tiles ^.^), of which 40x28 tiles are for the actual level/scene/game world. With 40x28 tiles you can build pretty detailed rooms, or wide areas, without the need for scrolling.
The interesting part for me was, that the tiles were not square, they were pretty unusual 16x12 pixel in size, transforming the whole level to a 16:9 resolution → 40 tiles x 16 pixel = 640 pixel in total, 30 tiles x 12 pixel = 360 pixel, perfect 16:9 format, therefore easily scaleable.
Multiply that by 3 and you get a 1920x1080 resolution, by 6 and you get your 4K, while all tiles fit perfect to all pixels.
What is your tile resolution? 3840 / 26 tiles = 147,69 pixels, that one seems odd, did i count wrong or misscalculate somewhere?
2160/15 = 144 pixels, that one works → 72 pixel at 1080, but are your tiles actually either 72 or 144 pixels in size?
)
