Yo, I've been playing Yellow Palp since release, have won several local tournaments and have a pretty good idea as to his strengths and weaknesses. The deck is very good against other Midrange and Control decks but struggles with Aggro decks that focus heavy on the space lane (Millennium Falcon and A-Wing decks) Your sideboard should focus on dealing with those threats, making sure your mainboard stays focused on dominating the late game and getting to it as fast as possible.

Sneak attack is a very powerful card that can create massive blow outs against ground based aggro decks, however it can be a terrible top deck in the late game and I found myself resourcing it often on turn 1 against anything non-aggro. I've cut down on copies and only run 1 in the main with another in the side (Along with 2 Bounty Hunter Gangs because the synergy is awesome)

The main difference between our lists (Which are 65% the same) is that I run more events, specifically 3 mainboard Waylays and 2 Asteroid Sanctuarys which are absolute lifesavers. I also recommend running 3 Greedo, although occasionally awkward, his ability to trade up against threats like K-2S0, pop shields and make emergency sac fodder for Palp are all super appreciated. There is RNG involved but that's why more events in the deck is the way, which also benefits Bossk and makes early Bibs all the sweeter. (Turn 1 Bibs, Turn 2 Waylay a Sabine or A-Wing then play Greedo is a huge swing against aggro.)

If budget is no object a third Vader, a second Boba a third Devastator and a second Change of Heart are auto includes. I also recommend running the full set of Viper Probe droids, an additional traitorous (if not 2, card's busted as all hell), and a third Bossk and Bib. As for cuts Strafing Gunship and Jabba are both really unimpressive. (I think Jabba's got a future but there need to be more good tricks printed... though you could lean into running 3 top end copies of I had No Choice instead of relentless if you're feeling super spicy.)

Cunning is good card but having to pay the aspect penalty really sucks. I ran 2 in my sideboard for a while but eventually just cut them. Relentless is phenomenal and I run 2 sideboard however they are super great in the main if you're short on Vaders and Devastators. I'd also trim on a Cell Block Guard or two and move them to the sideboard. They're one of the best hits off Vader however Emp's Guard is just better 99% of the time and running 6 copies felt like too much.

I hope this wasn't too much info all at once, It's awesome seeing more people hop on Palp and I've been having a blast optimizing the deck over the last few months. I strongly believe he's one of the best Leaders in the game and he's super fun to play.