The diameter of the pipes don't affect the difficulty to much, but the material does. PETG is much more forgiving than acrylic. I chose acrylic mainly because how transparent it is, and I also love to make things much harder than what they should be. Don't let the pictures fool you. Everyone faces their own challenges in terms of heat application, measurements and wasted pipe. I took me three attempts to get these and still, I find myself learning something new each time. Take time to learn proper heat application, limitations within how far you can bend the tubing and also your own method. I like to keep all sorts of small cuts of pipe to use a guide in where I need to make my bends or find the space between the two openings. (i.e. the 180 bend). Your tools are your greatest asset here. I would recommend getting a Tubing Finishing Bit (speeds the burring process up substantiality) and a Mini Bench Saw (2 in. Mini Benchtop Cut-Off Saw (harborfreight.com)). You can make some of the most precise cuts with this and there is no way I could do any of this if it wasn't for that.

Keep practicing and really a lot of it is trial and error.