Help with tracking subdomain used for Adwords campaign

I have a WordPress website that has Google Analytics set up(using Google Site Kit Plugin) and have now finished setting up a subdomain that also uses WordPress.

The purpose of the subdomain is to be used as a Landing Page for Adwords Campaign. I want to track this subdomain using Google Analytics to see my progress. This Landing Page is purely for Adwords and therefore has 'noindex'.

Now here is where I'm getting confused/problem: Apparently GA4 can track subdomain activities. But to make this work, my understanding is that I need to use the same Measurement ID from the Data Flow of the main website to the subdomain. So I tried to install Google Site Kit plugin again and use the same Property(GA4), but the plugin is telling me to connect a UA property which I allowed. When I finished setting it up I see it created a new Data flow using a different Measurement ID.

All I really need is to be able to track the subdomain landing page - see how many clicked from the Adwords campaign, how many clicked the contact button/WhatsApp, filled out the contact form, etc. If there is a simpler/better way to do this then please help me out.

Thank you for your help!