main domain for hosting plan matters for seo or other?

for years for my hosting account one of my domains was main domain (say domain 1) and i had other domains as separate folders under it, say domain 2, domain 3, domain 4 etc… my main website is domain 4, not domain 1. in fact, domain 1 was just a place holder static site with no activity or usage at all.

now i will change my hosting plan and i can choose another domain for main domain in place of domain 1.

should i choose my most active site ( e.g. domain 4) as main domain, and list other sites under it (such as domain 2, domain 3, domain 5 etc…) or even if i choose another inactive domain of mine as main domain it doesnt matter? i just cannot choose domain 1 anymore (dont ask why, it will confuse you unnecessarily)

please answer in terms of SEO, security and performance. i think it doesnt matter what domain i choose as main domain for my hosting, whether most active or an inactive site. am i right?