You are going to a million opinions here 'cause it is like bait fishing mythos.
>>1. where is the best location to put swarm traps?
My experience: about 50-100 feet from the existing hive in a mostly sunny location facing east or away from my prevailing wind. Book learning -- at mid-height in a tree. (My traps on a 3' stand work just fine).
>>2. anyone have plans for a tbh swarm trap or would it just be a nuc tbh or mini tbh?
My preferred trap: A double stack 5-frame Nuc with medium frames just in the top. (see pix). The would be easy to use TB frames with. However, the old comb scent is key in my opinion, so you want old comb from somewhere. The bees build from the top down, so medium frames work for the average sized swarm when hung from the top, sometime I get burr comb off the bottom with giant swarms. I use one old comb in the center, and new foundation on the other four. So failed traps with moth only attack a single frame. We don't have SHB so management for that pest in traps is unknown to me.
The incredible research by Dr. T. Seeley clearly shows a 40 Litre trap is preferred over smaller unit sizes - hence the double stack. His video tracks of scouts show them measuring the cavity.
>>3. does lemon grass oil work as a swarm lure?
Yes, scout bees will investigate lemon grass scent almost immediately, literally within 30 seconds of you placing it. But old dirty comb, or propolis scrapings is even more powerful.
>>4. how long do i leave them in the swarm trap to make sure the queen is mated?
Using a nuc trap, means I leave them in the nuc until the first brood cohort is capped. Also means the nuc is good for 6 weeks without checking, and then to transfer just lift the frames out to a box.
I build my nucs with ply long sides, and 7 1/2 inch fenceboard end boards. Means I can screw through ply into endgrain of wood for a strong and serviceable butt joint. The ply is whatever scrap I scrounge.
>> 5. is it to late to start swarm trapping in alabama?
(See local knowledge). My area has a primary swarm the last of April- first week of May. Swarms then drop off abruptly. Secondary swarms are more likely virgins or other mistakes. The late swarms that do take make great hives
the next year, as they overwinter with virtually zero mite or other issues built up. I feed late swarms syrup and pollen to get to 8 frames of bees by November.
>> 6. how hard will it be to find and kill a queen if its ahb?
Don't know. I have AHB locally (not dominant but present), and have requeened and split hives that were aggressive, but only when the behavior became apparent (after the hive is 1 or 2 supers tall). A swarm and a young hive won't be defensive (in my experience), so you don't really know about the AHB trait. The behavior manifests itself as the hive builds up. I don't know about the quick assay that carefully measures the length of the forewings.
>> 7. what type of lemongrass oil do i get food grade or lemongrass oil for aromatherapy
Definitely into fishing lure mythos here-- the active ingredient is also in Rose Geranium oil, etc. Aroma therapy oil beautifully works to draw scout bees, but see comment about old comb being a stronger draw. I mixed oil with crisco to prevent evaporation in the past and put in perforated lunch baggies. But recently just mist the entrance with sugar/lemongrass/lectithin (emulsifier) with a spray bottle. Seeley Webinar on Swarm selection