If they're going to make mechs, they need to be fast and agile, like in Armored Core, or Daemon X Machina Titanic Scion. If they are slow, then like in Supreme Commander, 4-8 legs, multifunctional giant spiders.
I'm no engineer, but I think mechs with legs like this should theoretically be very fast and fly high. Plus, it looks really cool:
https://platform.theverge.com/wp-content/uploads/sites/2/chorus/uploads/chorus_asset/file/7273573/millspecBT01.0.jpg
4.
https://www.reddit.com/media?url=https%3A%2F%2Fi.redd.it%2F3fhr026bwus31.jpg
5.
https://www.pinterest.com/pin/119486196342540773/
6.
https://es.pinterest.com/pin/45880489939680011/
And giants can be like these:
1.
https://static0.srcdn.com/wordpress/wp-content/uploads/2019/09/Daemon-X-Machina-Spider-Boss-Battle.jpg
2.
https://media.moddb.com/images/downloads/1/185/184260/supcom_thumb.jpg