Activating HSTS on your server, good idea for rankings?

Hi there, I currently have SSL on my money site. I have done numerous audits (including SEMrush) that state that I should activate HSTS to force browsers to open the https:// versions of my site rather than the unsecured www. and .com subdomains. I currently have 301 redirects doing this. Wanted to know if this is a truly a good idea that will help my rankings or will it just potentially just screw stuff up? Also I have read that even if you do HSTS then 301s should remain, is this true?

Here is what SEMRush says:
HTTP Strict Transport Security (HSTS) informs web browsers that they can communicate with servers only through HTTPS connections. So, to ensure that you don't serve unsecured content to your audience, we recommend that you implement HSTS support.

Moz: Implement HTTP Strict Transport Security (HSTS). This response header tells user agents to only access HTTPS pages even when directed to an HTTP page. This eliminates redirects, speeds up response time, and provides extra security.

I will tell you the problem I had with implementing this. Now in order to have this working and being added to the preload list, I was forced to have every single sub-domain I had created in the past to have it's own SSL certificate. This could get expensive depending on how many subdomains you may have and really depends on your setup. I would have cost more than what it was worth for me to buy SSL certs for every subdomain that I had, so I deleted them instead. Honestly this killed my traffic on this specific website and it's to the point where I'm considering removing my website from the preload list and although a big pain in the ass, maybe I can recover my rankings.

So if you have a setup like I do, really think about whether this is right for you, I didn't see a huge jump in rankings but that may just be the result of deleting my subdomains, which were 301 redirected to certain posts I had. For myself and with respect to my website this was a huge mistake and apparently it is possible to undue, it is a huge pain and knowing my specific setup would never do this again. If you don't have subdomains then you may see benefits, my main issue is that I had built links to some of my subdomains this is what likely killed my rankings on that website.

I am going to likely rebuild my subdomains and remove this website from the preload list but this could take months and is not guaranteed, so my suggestion would be to wait for more opinions, before you decide! Hopefully someone who did this properly and can share their experience chimes in, good luck.