You are correct no spell token graphics provided with the extension. You need to provide your own or grab a pack from a different source.
( I normally link the 5e pack on DMsGuild, But with you talking about PF 2e I'm not sure of any specific packs for those spells. If you use a 5e pack you might have to hand edit the definition file in the art pack 'mod' file to set the 'ruleset' to 'any'. For the spell token graphics pack to show up outside 5e. )
Not sure on your 5 feet to 1.5. I'm assuming you are talking 1.5 meters ?
The extension does not change the map settings, but the extension does have 'suffix' support so if you change the map grid to '1.5' and set gird 'suffix' to 'm', it should then correct scale a spell token to that map grid size configuration. ( ie normal 5 foot per square map with a 10 foot spell token would take up 2x2 grid squares, and if the map grid is configured as '1.5 m' per square that same 10 foot configured spell token will still take up the 2x2 grid squares. )
Hope this helps, Pete