What is the difference between DevOps engineer Vs DevOps consultant Vs DevOps architect?
An architect is somebody who thinks and creates designs.

A consultant is somebody who gets hired for things like "Teach us how to do so and so", or to answer questions like "What's your opinion about this design?".

An engineer is the one who is objective oriented and pragmatic, something along the lines like "How can I get that design (created by the architect, and validated by the consultant) implemented and make it work"?.

Their salaries may vary (there are cheap and expensive ones), same for seniority (there are juniors and seniors, while everybody starts as junior, not all of them ever make it to senior). And job demand is pretty variable (by region, over time, economical factors, depending on hypes, etc).

BTW, it doesn't really matter what the actual "subject" is, it could be "IT", it could be "Road Construction", or it could even be "DevOps" ...

PS: What's in a name (or jobtitle), how about a DevOps BA, as shown in this post ...