Some notes the Attribute Boost vs Improved Physical Attribute thing.
+Attribute Boost is fantastic for Combat builds because most AGI skills are Combat Skills, and you rarely need the boost for more than a few turns in those situations anyway (combat is typically quick and lethal in Shadowrun).
However it always requires an action to set up (the drain is negligible so long as it's kept to Rank 1-2). But since you're limited to one attack action per Combat Turn, this isn't as big an issue as it was in prior editions.
-For non-combat builds, Attribute Boost is much worse in general. It can't be used for any Extended Tests because the duration is so short.
In your case, it's useless for bolstering Sneaking and Lockpicking because those tests are ongoing. (you don't suddenly stop sneaking just because you made it past a camera, guard or other witness, and any non-trivial Lock Rating will require an Extended Test.).
It's usable for Palming, albeit a bit dicey with only 4 turns or so (24 seconds) on average. Depends on how strict your GM is about the timing and the nature of the Palming attempt.
Random pickpocket or plant job in a crowd? Easy.
Getting close to Someone Important (TM), especially in a "public" venue or place with plenty of witnesses? (possibly a corporate party) That requires a solid distraction or Con Test to get an opening.
12-24 seconds may not always be enough; so don't assume Attribute Boost will always work there.
Of course, being creative and improvising is always your best option as an Infiltrator; far more-so than just relying on gadgets and powers. I played a very similar kind of Adept for years, and it has always been the least rote and the most fun.
+Improved Physical Attribute actually improves the attribute as if it were an Augmentation (and counts towards your Augmented Maximum).
Since you're starting with maximum racial AGI, Improved Physical Attribute is a REALLY GOOD long term investment. But it's super pricey.
Another option is to combine the two at Chargen.
Take Improved Physical Attribute (Agility) AND get a Rating 2 Qi Foci (Tattoo) with Attribute Boost (AGI).
The Foci costs 6k Nuyen and 4 Karma to bond (total equivalent Karma Cost of 7; much cheaper than Initiation!)
For 14 Karma equivalent (or 12k Nuyen + 8 Karma), you can get two such Foci: One for STR, and the other for AGI; and you can switch them on/off as needed to stay out of Foci-Addiction range.
(BOD and REA are bad picks for Attribute Boost, for reasons I won't get into here)