Hi LandLover
The language of post is indicating lots of questions & doubts with good reason. Therefore I wouldn't even consider big or small school but go and get a Class One medical as you can't be a commercial pilot without one then book some PPL flying lessons at your nearest flight school to see if you like it & get some honest opinions from your instructor on what your flying standards are like.
No direct experience I have only heard positive feedback on ACS. Whatever you do don't go 'integrated' with a so called big school, unfortunately what was once some highly respected schools have just morphed into over-priced pilot factories. Search these forums you will find lots of information. You will find a number of posters (Me, Rudestuff, Alex Whittingham, Gengis?) have been around more years than we care to remember but listen to their advice.
RichardH (Retired ATPL theory instructor at big & small schools).