An isolation transformer only offers a very minor increase in safety, and
ONLY if you know exactly why that is, and understand exactly what you're doing.
In some respects it can be
MORE dangerous for those who don't understand it, as it gives them a false sense of security, only offering any advantage at all for a small number of specific situations.
In my previous career as a TV Bench Engineer I built them in the service benches (twice, in two different locations), as there 'may' have been a legal requirement for them - it's a bit of a vague area, so we did it anyway.
Personally, at home, I once borrowed
THREE (for a specific purpose), and gave them back afterwards - even though I was free to keep them, and they were nice 1000W versions. I later turned them down again, as well as a number of 500W ones.
Where I work now we don't have any, and have no intention of getting any.
My point is, if you have to ask, and don't know
EXACTLY what they do, and how they
MIGHT help, you probably shouldn't be playing with them.
Incidentally, the various International Manufacturers training facilities I've been on courses at, have never had isolation transformers - and I did once blow a load of parts off a board with a scope