Hello, after researching from various source, many said that unless it is custom loop, aio cooler actually worse than air cooling. Is that true for evga RTX 3080?

Hybrid/AIO cooled cards are better than air-cooled cards is a general statement.
 
That depends so much on airflow, settings, and other factors that generalizing it is unwise.
 
I had a 3080 FTW3 Ultra that once I got it tuned with a nice undervolt, good airflow and all that noise, combined with my 70F ambient, was running at 50-56C in games... and that card was air-cooled.  But that, again, was with an undervolt, which makes the card draw less power, and thereby run cooler by generating less heat to begin with.  This is even more effective on Hybrid cards.  As a for instance, my Kingpin (when it still had the AIO/Hybrid cooler on it) could run at 2100MHz at 1025mV, and 2160MHz at 1068mV - both of those resulted in lower than stock settings temperatures in games, while giving better than stock performance (because stock boost clocks settle at the 2025-2055MHz range on the 3090 Kingpin).
 
The truth is, Hybrid or Air cooling should be a choice based on what you want out of your build, and your plans for it, like if you want to go liquid cooling open loop eventually, get a HydroCopper card, if you want silence, Hybrids can be better than air as long as you don't have a pump noise issue - but right now, it's a "get whatever card you can get" environment for most of those seeking a video card.
 
Things like your ambient, airflow profile, case setup, and future plans all matter when choosing air or hybrid or whatever else.  If you have a high ambient room temperature, or poor airflow, a Hybrid can actually perform the same, or worse (if there's lack of airflow) than an air-cooled card in the same situation.

Many different variables but if the AiO CLC is well designed/engineered and installed properly, it should be better.

almost did the hybrid thing but stopped, just more possible problems for little gain. 
 
i'm not going to underclock my (hotter than i would like) 3080 because it has a three year warranty and i know where the ups store is. 
 
but another p/p could mean two more argb fans...? (already have a modded 2/140 rack on top)

Difficult, but should work

Realistically it depends on a lot of factors, as others have pointed out, like airflow and what kind of operations you're running on it. AIO does often offer a compelling cooling solution if done right, although in my experience air has also been sufficient when done well and not pushing the OC too hard (YMMV)

Good air cooling is comparable to good water cooling. Water just has the ability to draw more heat into itself, to it has a higher threshold for performance. It can be harder to work an AIO for both your CPU and GPU, which is where an air cooler may come in handy. 

I've heard that good airflow can produce comparable or better results than water cooling. 

Each one has + and - `ses.

100% water is always better than air, keeps it much cooler.

Liquid cooling is better then air.
Just think, expose your arm on 10 Celsius air temperature or 10 C water bucket.  
 

I'm seeing a lot of people that are getting high VRAM temps with the hybrid cooling 3080s. I'm wondering if the chips aren't getting enough air flow, since the coldplate is only on the GPU, and the rest of the card's components are cooled by a smaller heatsink and only one fan. Meanwhile on the air-cooled cards, the VRAM shares the same heatsink as the GPU and has two or three fans doing the work cooling it all. There's also some talk from 3090 owners that have trouble cooling the VRAM on the backside of the card, which lends further credence to the idea that they need some strong active cooling.

i think not, let air coolers stay

I personally like air cooler, so I don't have to worry about leakage.

The only Downside to AIO is space in your PC case.