hello my beloved anon !! :D i will briefly explain everything regarding my banners rn in the best way possible !!
for my full fic / one shot banners (like my brighter days inc & surprise one) i use canva !! to get the size right (i use twitter header templates / size for them except for surprise that’s the only one i didn’t use it for) to get the filtering of the colours i want correct and to get the fonts right as well !! when it comes to the fonts of the texts i usually alternate between canva & phonto (surprise was in canva while brighter days inc was in phonto !!) for me phonto is somewhat easier than canva bcs it also has a download fonts feature in it to give u more fonts to work with !!
i usually use twitter header templates for my hard thought banners & for my full fic banners as it looks better that way in my opinion, but for my timestamps i use either picsart or ezgif (which is a very helpful & free website !!) in resizing the images !!
i also use my own photos app edit feature when it comes to editing the filtering of the photos & i usually edit the exposure, brightness and saturation amount !! i also do the exact same things in picsart as well it just depends on what ur feeling at that moment :]
i hope this was helpful to u in some way and if u have any other questions then i’ll be happy to answer :D