You're not confident in the tool you're using to level your rig.
Do it right once, and you'll be confident in your "field" levels.
As others said, use a 4' framing level for fore-and-aft leveling. These can be too long for side to side (on the floor when you can see them, but a 24" carpenter level is a nice addition to your home toolbox, so you can use one to level side-to-side.
Setup in your driveway and use the construction levels to get it perfectly level.
Next, get your Hopkins levels, or whatever you wish, and attach them to the outside of the rig. Attach one to the side of the rig and one to the front where you can see it.
Important: Choose the brand you like (I like Hopkins), and attach them with STAINLESS STEEL sheet metal screws - in addition to the double-sided sticky tape. This way, not only will they not fall off, you can also remove a broken level and replace it without the reenacting the carpenter level nonsense. The stainless steel screws won't rust in place, and the holes on the same brand of level will be in the same place to install the replacement level in its "calibrated" position. No muss, no fuss.
My preference is to mount the front level INSIDE the A-frame where it is out of the line of fire of the TV tires, and the A-frame offers some protection from the harsh realities of the road. This depends, of course, on whether your setup partner can easily see the level while safely out of harm's way while mounting up on your Anderson Levelers or whatever you use. If not, and the one on the front frame cross member gets broken, the remove and replact takes a couple of minutes.
The one on the side can be anywhere, but I put mine very close to the front so I don't have to run around much to see it when setting up on my own (often the case when I put the rig away after coming home.
I like the Hopkins levels for another reason...the nice straight edge on the bottom. You don't even need to mess with leveling the rig side-to-side if you use a block or similar straight edge bucked up against the bottom of your frame cross member (assuming it's not tapered). Just rest the bottom edge of the Hopkins on your block, and voila, you're level. If your frame cross member isn't straight and level when the rig is level, you have bigger problems.
Fore-and-aft leveling is, in most cases, as easy as raising and lowering the tongue jack until your carpenter bubble level is happy. Then mount up the Hopkins to agree with the framing level.
My recommendation - Hopkins Levels:
https://smile.amazon.com/Hopkins-085...sr=1-1-catcorr
There are other good levels out there...you can even pay a ton of money for one, but if installed properly, the Hopkins levels have a nice, long, gradual arch to the vial, so quite a bit of precision is possible. Other levels, with much more aggressively arched vials are actually less precise.
Also remember that leveling an RV is "Gubmint" work...as in "close enough for government work. Perfection is possible but unlikely...especially side-to-side. The main goal is for the evaporator fridge to work and to not have stuff slide off the table.
These levels CAN get you "perfect" if installed correctly, and they are large enough to show even small amounts of out-of-level. But side-to-side on the slopes of a lake shore or similar often requires a shovel to dig a hole for the uphill tires AND a leveling wedge for the downhill tires....see photo. Often, close enough is as good as it gets.
But THIS Hopkins level is NOT (in my opinion) the right tool for the job. I took the belt and suspenders approach on my previous rig (the ones recommended above and one of these, too), and this guy was never even close. One of these might get you into the neighborhood, but not in the ballpark.
https://smile.amazon.com/Hopkins-095...-garden&sr=1-3
I'm less fond of a level like this, because it's not sensitive enough. These work great on tractors and other machines to avoid tip-over, but the first graduation is 5 degrees! That is some serious tilt. And 15 degrees - the first marked graduation - is enough to have you fall out of bed.
https://smile.amazon.com/Sun-Company...sr=1-1-catcorr Some may like these, but the Hopkins is far more precise.
Once you install proper levels on your rig, you won't lack confidence in whether it's level or not. And if there's an optical illusion that makes it "appear" to sit nose high, you'll be able to ignore it knowing that a good bubble level doesn't lie.