Wallop, you’ve never seen a pro tiler working.
To so a decent job, with proper setting out, you will need both.
An angle grinder will do at a push, but its gar from ideal and won’t give you a good.
What so you mean by ‘bar cutter’?
There are two basic types, wet and dry. A dry cuttter is the manual type, with a scoring wheel and breaker.
Wet cutters come in two forms, most common and useful is the table variety, with a diamond blade that spins in a shallow water bath to cool and lubricate the blade and keep the dust down.
Any cutter intended for diy use wil not give you a decent finish, you world do far better to hire one.
My big dry cutter cost £330 and I’ve got a small one too. i’ve got three wet cutters got diffrent tasks worth about £500 in total