All,
UPDATE FROM ORIGINAL
I have found smatterings of good information in different posts on this board. There are some really smart HVAC guys on here. My updated goal is to provide a guide on the information that you should gather before reaching out to those posters. That way, they can provide help to as many posters as possible.

I have a 1950's home in San Antonio. We have approximately 2500 sq ft of conditioned space. The home struggles to maintain 74 degrees during the summer and we have one of the rooms were our one-year old sleeps that routinely is around 82 degrees. I am looking to personally do an HVAC audit to determine the following:
1) Do we need to redo the duct work in ceiling for better airflow?
2) Do we need to replace the entire HVAC system?
3) Do we need to replace the glass doors on the house?

Building
I have a 1950's home in San Antonio. We have approximately 2500 sq ft of conditioned space. The house is built on a 12" slab (that is what you get when they build the house at the same time as the airport). The roof is a low profile that presents extreme difficulty in accessing the attic for any human being above 5'5". I am 6'1" and it takes me approximately 30 minutes of crawling on my stomach to make it from our access point to the main portion of our house. When the house was re-insulated a much smaller person came to the home.
House Diagram 8.22

roof profile

The house is an L-shape with Glass Sliding Doors on the inside of the L facing East.

Insulation
The house was re-insulated in 2023 to R-38 level with cellulose.
Insulation prior to 2023

Duct Work
The duct work appears to be in good shape and the main plenum is insulated. The biggest concern with the ductwork is that there is one plenum where the two HVAC units push air into. I routinely have to patch blowouts in the HVAC closet.
The other main concern I have is that there is only one return that is in the central portion of the L.

Vent/Register 1101 square inches
Return grill 730 square inches

Ductwork

HVAC
We have two 3 ton units that are connected to the same plenum as a two-stage unit. One of the units is 20 years old. The other is one year old. I have them serviced once a year.

Audit plan
I plan to audit the ventilation system at the vents and return with an anemometer:
https://www.amazon.com/gp/product/B07J64TCBQ/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1

I plan to audit the walls. windows and returns for temperature with this thermometer:
https://www.amazon.com/gp/product/B00DMI632G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

There are several different free air flow simulators that I have seen on line. I don't know if anyone has anyone that they have used.

Updates:
Read a good post from P.H. Dexippus. The oversized A/C Unit post has some good discussion in it.

How old are the windows and glass doors? Keeping a house at 74 with temps this summer is pretty good. The hotter room I would look at getting some shade on it, replacing the windows or doors.

I am considering replacing the doors as I said they're all glass sliding doors that are not gonna be cheap to install. I'm gonna be curious to see what the temperature reads when I start shooting the house.

When we moved in my wife removed the curtains in installed pull down blinds that she really wanted. I feel like they do an OK job but definitely don't have insulation factor of the curtains.

If I do the glass, then it might be a waiting game for some of this inflation to cool. At that point., I'm also probably going to be looking for glass manufacturers recommendations because I have about 100 linear feet of glass wall and five separate sliding doors to replace.

Ben had his glass doors and windows replaced at a reasonable price at his new place if you want to send him a text. Similar size house, age and roof pitch as yours.

OP I'm glad you asked this. I've been wanting this same service done in SA and didn't know what to ask for. HVAC audit is exactly what we need, too.

I'll be following closely!

If you want to test CFM, you need more than a cheap anemometer. You can either spend real money for a calibrated unit like this cheap model or build your own and get close-ish results.

And I have a non-garbage infrared thermometer if you want to borrow it.

Those big 1950's glass doors are very leaky in addition to being poorly insulated.