Hi and welcome to the Forum.
The Numbeo website should answer your questions; this will take you to a comparison between Phoenix AZ and Glasgow. It talks about salaries at the start and you can change the numbers to make it more relevant to you; it also talks about other things like quality of life. My advice is to play with it and see how it works for you. Prices are a few months behind the curve, inflation is about 1% at the moment.
You say you're a mechanical engineer, then you need to make sure that any qualifications you have or use in your day to day working life are recognised in the UK. As for what base pay should you accept, you may as well ask us how long is a piece of string. To get a decent job anywhere you need 4 things:
Relevant qualifications
Relevant experience
Speak the local language
Luck
So you can do the maths yourself on your chances of getting work. You sound like you're already trawling the internet, that's as good a place as any. Only thing to watch out for is that much of what they advertise will already have been filled and is more to attract your interest and CV for future jobs they may have to fill - that's how the agencies work. Try joining LinkedIn, then reach out to your peers already in Scotland and ask them where the work is and how much the pay is. Local Facebook pages can be useful, I just had a quick look and it's a mixed bag, but some people are looking to recruit; it will depend on your skill set and experience.
Covid is causing havoc all over the UK job market. Many workers are either furloughed, or have lost their jobs altogether; the consensus of opinion amongst the gloomsters is that once the Government support stops at the end of the lockdown, that many more will lose their job; I don't share their pessimism, but somewhere between the 2 lies the answer.
Unless you are UK passport holders or 3rd nation citizens with skilled visas, right now you won't get into the UK as their is a travel ban in place at least until May and depending on what happens between now and then, may or may not be lifted.
The politics are not helping matters with the ruling party currently tearing itself apart after one half tried to get the other half's leader locked up in jail. Such items and an election in May with possible independence referendum on the cards do not instil confidence in business investors; so add that to the Covid issues and if you have UK passports, you may want to look south of the border.
Other than that, Scotland is a lovely place, lots of opportunities to do your trailing and walking and the environment can be awe inspiring.
That's about it. If you have any more specific questions, please come back to us.
Hope this helps.
Cynic
Expat Team