The way I look at the core books, variants, DMs Guild and free stuff that exists is that if those do not work as is, they may spark an idea of how you or your table would prefer it, s
o they can be customised to your preferences.
With regards to your specific issue with Powerful Build
As DM I would allow the feature to stand as is for weight purposes, but not necessarily for items that are bulky - so it doesn't matter how strong you are, you should not be able to move and fight perfectly while carrying several suits of armour, not necessarily because of their weight but because of their bulkiness. There are several systems that don't use actual encumbrance but bulk. You can even incorporate both systems at the same time.
Grit and Glory is a free pdf which I know looks at bulk but like I said there are others. I'd recommend you to see if their system is suitable or inspires you to customise it. You could even brainstorm this with your players as a group so they do not feel you're short-changing them on a class feature.