For the first two entries you highlighted in your screenshot, you would need to make sure the type is select (you have it for one, but you would need it for the other). Then you would need to follow the directions in the link above for select boxes. The remote datasource would be set up in the server action, you would need to create a new database connection to connect to the remote datasource.
For the datetime one, you would change the type from date to text, then follow the directions in the date picker above. There has been some discussion that you can keep the type as date and use the date picker, but I have found that changing it to text works better for me.
As far as the Ajax Select2 link you posted, that is not something that is native in Wappler and you would need to code that yourself. It may be possible to generate the form using Wappler and the change the code to include the Ajax Select2 field. You would need to follow the directions on their website to see how to do that.
As an alternative to the Ajax Select2, have you considered the Auto Complete feature Wappler offers? Using the Autocomplete Component