System landscape concept

I'm using almost every piece of fluent software available. Of course, I'd like to use it the right way and that leads to design questions for my system landscape. What would be your suggestions considering the following statements?

Wordpress instances:

• main website uses www.xyz.com (= currently the only website, all plugins installed there)
• landingpages should be hosted on a subdomain lp.xyz.com (for seo and performance reasons)
• community (at a later point) should be hosted on a subdomain portal.xyz.com (for performance reasons)

I'm currently trying to solve some challenges:

• booking calendars/forms should be available on both www. and lp.
• bookings should be visible in one central location (www. ?)
• forms should be available on both www. and lp.
• forms should be used to mainly signup into crm
• where should crm be hosted? (www. or separate instance)

What I could find out:

• sending signups from www. and lp. to the crm is possible (on of them via webhooks)
• booking into the same calendar is possible

The main challenges are:

• having forms available in both www. and lp. while having form entries in one single location
• having booking calendars/forms available in both www. and lp. while having the booking entries in one single location
• keeping all the instances as clean and fast and secure as possible

Also, I was wondering what would be the recommended setup. Having everything in one place (one server with enough speed and power) or is a distributed setup also recommended in certain cases? How about multisite setups, are these supported at all and how would I deal regarding licensing? You see, there's a lot going through my mind at the moment. So I'd appreciate any hint, recommendation, feedback - even stories about failed attempts to achieve comparable/similar scenarios would help (prevent the re-invention of wheels).

PS: I'm posting in this space to not scatter my topic across many spaces and confusing people too much. 😅