I have seen a lot of questions here on the u/woweconomy Reddit about professions, older crafts, and combinations of professions. Now I could answer every post or just make here one by explaining a couple of things and showing older crafts as profession set-ups.
To make one thing clear, there is and will not be a "best profession" in Shadowlands, some are a bit better (depending on the expansion, expansion timeline, demand, and competition on your realm) but overall, it's better to have them all. Even if there was a "best one" then the majority would go for it and it would become the worst profession.
There is also never a perfect combination of professions, it all comes to your own preferences. That is the best combination. Now if you ask what profession works better or is more efficient, then there are some answers waiting for you.
Keep in mind that my guides are based on what I think are the most effective ways to min-max production. It's not built when it comes to rep locked recipes. Getting the rep is temporary while having a good setup is forever. I also suggest some classes and races because of their racial trait.
Here are my guides;How to Setup The Most Efficient Profession Team
has a miro board
.Crafting Older Content
includes a miro board
and a TSM import string for the crafts.Alchemy Masters
includes a TSM import string for the items.
Don't just focus on what I am showing you. Try things out, look for other websites and content creators that have their ideas on professions. Keep in mind that there isn't a "best way or profession", it all comes to personal preferences, realm, expansion, and demand.
I hope this will give you all better guidance for making your profession choices.