Tooth still kinda grey after root canal with internal bleaching. Should I get a crown/ veneer to match the tooth to the others?

Without a picture it is difficult to determine the answer to your question without a picture. It is very possible to mask out the qrey caused by having a root canal. Also, a good dentist and lab should be able to accomplish this with only working on one tooth. The thing to know is that the tooth may continue to darken under the restoration and over time this darkness may become noticeable. The thing you need to understand is that this is a problem that will require maintaining for the rest of your life. Find an experienced cosmetic dentist to help you and you should have excellent results.

It is hard to say without a picture.  Your best bet is to go to a cosmetic dentist you trust and ask them the same questions.  They can give you your options.  With the amazing materials we have now I am sure they can help.  Good luck!