D&D 5E Should I dip either Fighter or Rogue for my BladeLock?

I'm on the fence about dipping for a few levels of either Fighter for the awesome stuff it gives or Rogue for Expertise, 1d6-2d6 SA, 1 skill and Cunning Action. I shouldn't do more than 3 levels actually. If I did 2 levels in each I'd lose some great Warlock stuff at upper levels of play...

What I was planning on doing with my Bladelock, who has a Charlatan background and convinces everyone he's a Baron, is to use the "real me" being a Tiefling Highwayman/Back Alley Mugger at night when nobody's around and just use my melee attacks & Warlock tricks to get the upper hand in duels & ambushes. Not using my Eldritch Blast in this "real me" persona of mine. Mainly doing things nobody during daylight hours has seen me do. Using Darkness spell to get the upper hand and cantrips like Booming Blade/GFB to enhance my melee attacks.

Once I get my hands on a Scimitar of Speed I'll be really looking forward to prowling the city for some thuggery.

Now both classes for dips offer a lot for the concept I want for both the Warlock Baron & Bladelock Thug personas. Rogue fits more, due to, well, it being a Rogue of course... but Action Surge and a Fighting Style also give me some nice stuff for surprise rounds. Cunning Action will allow me to possibly get more out of Booming Blade and +1d6 isn't that bad either for SA fighting whenever I've gotten Advantage on my side.

Any thoughts on where to go with this guy? Also do you think having 2 dips of 2 levels each in Fighter/Rogue would be worth the loss of my 17th & up Warlock abilities? OR just stick with the 2 to 3 level dip max of Rogue OR Fighter...?

AT/EK would give you 2 extra slots for low level spells. SA is strictly better than dueling style. Expertise has out-of-combat use. Arcane trickster 3 seems best.

My personal choice (which I'll be doing after I reach level 12 as a BladeLock) is the Swashbuckler archetype. It offers improved SA, excellent mobility, and adds CHA to Initiative, which is awesome for a Warlock. The Expertise feature is very good, and multiclassing into Rogue also provides a new skill from the Rogue class list.

If you want to emphasize the Charlatan background (I'm doing something similar) use Expertise for Deception and Persuasion.

Swashbuckler Rogue would be perfect, but I doubt my DM would allow the class. Probably will have to choose Arcane Trickster or Assassin if I go 3 levels. Swashbuckler is so mouth watering with those abilities.