I think @Tory said it best. There are pros and cons and as @Chris and @Adam have pointed out there are very certainly tangible benefits to starting your career early. That being said if you are even considering a gap year in the first place chances are there are also very tangible benefits for you to take one…
I graduated HS in 2018 with 30 college credits under my belt already, so effectively my freshman year was complete. I was a bit of a wreck at the time and while I loved backyard engineering/tinkering, I didn’t really think that engineering was the right path for me. So I took the year, worked my butt off. Ended up chasing hourly pay for the year and in doing so worked in an auto shop, at Starbucks, babysitting/lawn care, and eventually at Chocolate distribution plant (don’t ask me how that happened haha). During my time working odd jobs I met a Delta pilot who turned me on to aviation. Took a discovery flight and immediately knew that this is what I wanted to do.
Saved up all that time and come December 2018 I hopped on a flight to Iceland and from there went on to Spain and Italy (did work stay arrangements in each, still had time to be a tourist), then onto Japan, Fiji, NZ, before heading back stateside to work on my PPL at a mom and pop shop. During my time overseas I began my studying early so that way when I came back I could just knock out my Written and then hustle through training w/ minimal ground.
A gap year is a REALLY REALLY EASY WAY to burn a year. Like, really easy. The number of people I’ve met who said they were “just going to spend 1 month” and then it turned into 6 is too high to count. That being said, it’s also a great opportunity to better yourself as a person. Nobody wants to get on a plane with a frazzled pilot, and certainly you don’t want to BE a frazzled pilot throughout your training. And it’s up to you to determine if you really need this time off, or it’s just for “funsies.” My year was a great opportunity for me to work on people skills, work ethic, and figure out what I wanted to do with my life. And working garbage 9-5 jobs definitely was a good motivator for getting a good education that’s for darn sure 
anyways…
After my gap year I got my PPL and went straight to Auburn University. @Adam caught my little slip up there w/ my Flight Major statement. I’m still breaking a few thought patterns I developed in going to a 141 University haha. After earning my IR over there I ultimately decided to leave for a number of reasons to include cost, 141isms, and training structure. I came over here to ATP and while it is pricey, it’s nowhere near as bad as ERAU or AU or any of the other prominent 141 University programs. I’m a custom program at ATP and I’ve thoroughly enjoyed the training so far. Currently I’m a CFI working on my CFII.
Once I complete the program here I intend to get a CFI job and continue online with a Bachelors in Aviation Management from Middle Georgia State University. I figure all of my credits taken elsewhere transfer into this degree so I might as well continue w/ the aviation college degree anyways. I know of an instructor who’s currently doing this with Metro State here in Denver and he (a bright dude) told me it’s pretty darn difficult to manage. Unfortunately I don’t really have much of an option here so I’ll follow in his footsteps and make it work, even if that means taking classes part time.
There are definitely pros and cons to getting your PPL elsewhere. I’ve seen many of my fellow students who’ve done the full program at ATP “get it” a lot better than those who’ve come in from elsewhere. They mesh with the program quite well because, let’s face it, the program is where they established all their habits. For me, I don’t regret my choice to get my PPL at a local place and my IR at a university. I think the variance in training styles acted as another learning experience for me. I can’t say I’d recommend it to others however. If you can help it, I’d try to get your PPL at ATP. Always nice to train in nice well kept newer planes from the get-go 
Hope I helped, Mohsina!
TL;DR Try to get your degree before you come to ATP. Gap year is an entirely personal choice that in the long-term will effect seniority at whichever airline you choose. And I’d recommend shooting for PPL-MEI all done @ ATP if you can help it.
