I think you have your answers. Doing a dummy glue-up for the experience is probably a worthwhile investment of time and will help you get the idea. After some practice, unless something goes wrong, a card scraper will take care of any minor "oops" in alignment on a glued-up panel.
Many glue-ups exceed my planer's 15" capacity so using it as a fix is only partially viable. Changing thickness on parts in the middle of the build causes its own set of issues. If you are trying to decide on one or the other, I would recommend a good quality planer. You can edge-joint boards on the table saw and face joint boards with a planer sled.
The planer/sled/tablesaw combo can get you by for quite awhile. You will understand better what you plan/want to do and what types of pieces you are drawn to after making some items. Once you have a better idea what you are going to like doing, the importance of certain machines will become clearer. This really helped me focus where to spend my precious tool dollars.
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke