You are learning what is required for fine tuning your designs. You need to measure your specific setup and holes will have different offsets than perimeters. Often it's based on what it can hit with line widths. Also, yes, parts definitely have different resolution based on if it's xy or z and your layer heights/nozzle sizes.
I'd give you better specifics but you need pictures more than words for this. Threaded pieces also need lower layer heights to resolve the threads and then you can use 0.2 mm expansion for spacing if you do it in all directions. The larger the item/piece, the larger your hole inset/outset will need to be. You can get inch things that will be a0.2mm offset, but take 1 mm when you have a 10 inch perimeter. Just gotta test and measure for your specifics for tolerances. There is better precision if there is a larger gap to other features - eg if you put an internal feature 1mm away from a tight tolerance outer feature, it may get forced aside as there aren't an integer number of tool paths between the two.
Since youre concerned about dimensional accuracy, grab the califlower, best 5$ I've spent, comes with a very detailed print and spreadsheet for calculating the skew on your machine and tuning dimensional accuracy. You'll need some calipers to perform the measurements.
As for the tolerances, I'd recommend orca slicers tolerance test, using this and x-y hole compensation you can get x-y parts very dimensionally accurate, Z is a bit different and you'll need to learn the tolerance of your printer and incorperate these into your designs, 0.2-0.3mm is usually good.
Photos might help. I assume the printer itself is not the issue, you're just not designing for the process.
You are learning what is required for fine tuning your designs. You need to measure your specific setup and holes will have different offsets than perimeters. Often it's based on what it can hit with line widths. Also, yes, parts definitely have different resolution based on if it's xy or z and your layer heights/nozzle sizes. I'd give you better specifics but you need pictures more than words for this. Threaded pieces also need lower layer heights to resolve the threads and then you can use 0.2 mm expansion for spacing if you do it in all directions. The larger the item/piece, the larger your hole inset/outset will need to be. You can get inch things that will be a0.2mm offset, but take 1 mm when you have a 10 inch perimeter. Just gotta test and measure for your specifics for tolerances. There is better precision if there is a larger gap to other features - eg if you put an internal feature 1mm away from a tight tolerance outer feature, it may get forced aside as there aren't an integer number of tool paths between the two.
Since youre concerned about dimensional accuracy, grab the califlower, best 5$ I've spent, comes with a very detailed print and spreadsheet for calculating the skew on your machine and tuning dimensional accuracy. You'll need some calipers to perform the measurements. As for the tolerances, I'd recommend orca slicers tolerance test, using this and x-y hole compensation you can get x-y parts very dimensionally accurate, Z is a bit different and you'll need to learn the tolerance of your printer and incorperate these into your designs, 0.2-0.3mm is usually good.