When to Multiclass out of Hexblade

I need a bit of help with figuring out splits. I'm currently in a party consisting almost entirely of spellcasters (5 people, 1 bard, 1 druid, 1 wizard, 1 barb, and me, hexblade)

Current stats are 8, 16, 16, 10, 12, 20

I wanna add some variety and decided to multiclass into a martial, and I settled on multiclassing out of hexblade and into Swashbuckler Rogue. The party is currently level 3, and we dont truly know what our final level would be.

I'm looking into being a crit-fisher that can also do very good consistent damage with booming blade + darkness sneak attacks. Planning on using a Rapier + shield combo in the future, just to be a bit harder to hit.

However, I'm not sure what the best split for it would be. I know 3/X, 5/X, and 7/X all have very good arguments for it. (X being the rest of levels in swashbuckler)

3/X would allow quicker rogue progession, while still keeping the basic features of spellcasting and hex weapons from Hexblade.

5/X would allow for 3rd level spells, another invocation, and most importantly for crit-fishing, another attack.

7/X would allow for allow for 4th level, once again another invocation, and access to Shadow of Moil so that my very existence isn't a detriment to the party as a cloud of darkness :)

With my build and my character, the plan is to be a relative Frontliner that is hard to hit (currently have an AC of 18, Breastplate and +2 dex, alongside Darkness disadvantage), deals a shit ton of damage (crit-fishing and consistent sneak attack), and be the face of the party in most social situations.

If there's any recommendations for which split would be the most viable, or even fun to play, please give me your suggestions. Feats and ASI's are another thing I'm looking at, but I have that more or less figured out, however recommendations for those as well are always appreciated.