I agree with Evolutionary, that you should check the popularity of your engine. It is only a question of time, that you will have to look something up and then its helpful, when it has already a big community with many questions already answered. I have the feeling, that Pico-8 is a bit hard for to find answers.
Most engines will have a coding option. So your assumpttion, that GameMaker is ui only, is not correct. You can add your own code to it. It is a bit tricky, what to recommend, as the ui will do the better job, when you are new to it, but if you want to get the last performance out of it, the code option is better, but then you have to be knowledgable enough, how to do so. So maybe configure the basics with the ui, like drawing the tileset, and do the logic of a tile via code.
If you plan to move to another platform, i would recommend to do it from the start. As migrating a grown project can be troublesome and you have to figure out again, how thinks work. If you do a fresh start, then moving is no issue.
Also a hour a day sounds not to much. I dont want to discourage you, but you should then focus on using templates instead of doing all by yourself. Im not sure, how deep you want to dive, but i would not recommend to do everything at the start by yourself. Use the ui where its simple, if it gets more complex, check for templates for free and only after that code your way to it. But of course, if the developing journey is what you like to do, feel free to ignore this advice. Only if you want quick results, then this advice is helpful. You will soon enough learn, that game programming needs lots of time :P
I think arkanoid is a good beginner project, so go for it.