You might want to use individual subdomains for the most part. A few things to note:
1. You will need to get a wildcard cert and use wildcard DNS entries if you don’t want to go crazy with managing tons of certs and configs
2. With guards to security, browsers consider different subdomains to be separate sites and will disallow ajax requests between subdomains and the root domain. This helps with security, but makes ssl/sso a little harder in that any authentication has to know how to forward back tokens to the correct subdomain (a lot of auth solutions just forward to a single domain which won’t work).
3. By host mapping, I’m guessing you want to do some kind of semi-white label solution where you use the customer’s domain? This is trivial with subdomains since you can have the customer add a dns cname entry to their domain that will transparently forward traffic to your own subdomain. You would also need a small modification to your web app (also trivial for most web frameworks).
4. To do a custom host mapping without a subdomain would require a browser redirect - customer types in “support.customer.com” into their browser, the customer’s servers would have to receive the request and reply with a 307 redirect, and the customer’s browser would then go and load “blitzz.co/customer/”