If you want to make a top down 2D movement game, then learning RPG Maker is a good idea.
If you want to make a visual novel, I recommend starting by learning Ren-py. Ren-py is the game engine that most popular visual novels here use, and it's specifically built for visual novels. It's also much easier to learn than most game engines.
As far as the art style of the game you mentioned...
https://f95zone.to/threads/lateshifter-v1-2a-oko.2437/
You have a few choices:
1) Find an artist to partner with. - Risk that they may drop out
2) Pay an artist - Costs money
3) Learn how to create that art - May take a while
For option three, I'm not sure how they are creating that art. To me, it looks like it may be 3D models put through a pixel art filter. To do that you could learn Daz 3D or Honey Select to make and pose the 3D models. If it's not 3D models, then there are plenty of traditional art tutorials online and you could spend time practicing. You could also message the Dev and fans of the game to see if any one knows what software he uses to create the art.
As far as the tile art, you could replicate that in any paint program.
Good luck!