Google gives general guidelines about how to make good landing pages here.
Sadly they're not specific so you've got to try something and wait a while to see if the landing page experience and quality score improves - the "try and wait" approach.
There is one place you can get a definite answer: PageSpeed Insights.
Google hates slow websites. PageSpeed Insights is a free tool from Google that'll tell you what you (or the person who builds your website) can do to make your site load faster on both mobile phones and computers.
Making your site load faster often improves your landing page experience and quality scores. Fast websites also convert better than slow loading ones.