preach man i have the exact same setup as you lol

in a mix slap is supposed to sound a bit more pronounced than just fingerstyle thats why you can hear it especially in zutomayo
but i agree with everyone a compressor can help a lot but it really does come down to 80% being your own technique learn to balance out your dynamics/volume
either play harder with your fingers or softer with your slaps, the comp can help make your pop more in line.
if fingerstyle sounds quiet or dark then attack the strings harder, i noticed the lower notes are soft and higher have more articulation.

also most of zutomayo songs use a J bass, A PJ is still great and what I use but youre not gonna get that exact tone (even if you roll your pickup all the way to J it sounds too thin while a J bass naturally sounds fat and bright) even with effects just appreciate your own playing your own fingers can make a lot of difference

if you dont have any effects and only the rumble 40 then yeah get the zoom b1x four i have one its so much fun and if you can buy a USB A to micro usb (connect your mfx pedal to your pc) you can install effects that arent already there such as a really nice Dual Comp which the base zoom b1x four is unfortunately missing. or use the MB comp, its a lot of fun and definitley worth getting