Some sites have a lot of icons but either cost money to customize or just look cheesy. Here's are my favorite places for free customized icons that look great and they all give you SVG files too so you can open them in Affinity Designer and edit them. Note: Affinity Designer is way better than Illustrator and is a one time purchase. :)
This has the most different icons and you can select 6 types of weights and colors include a preset duotone. This is crazy helpful. You can easily download them in SVG and edit them how you want.
Not to be mistaken with AngularJS in any way - this is just a great place to get a variety of icons. Some pack cost money, but lots are free and they are still a reasonable price. I went ahead and bought them, because I love how clean their icons look. This also has good icons for social platforms.
There's a wide variety of icons here, but not quite as many as the other sites. It's awesome because you can choose the cap and corner styles along with the color, weigh and even size. So plenty of options! This site pairs very well with the others. If I can't find something here then I look at the others. Or if you're a collector of icons you can just download them all in one click and it will comes with a bunch of different file types.
This site has a fair amount of customization and many icons, but some of them do cost money. If there was a social icons I couldn't fins it found them on here for free.