I think if you are having difficulties with 50% PG trying different kits supplied with MTL type coils designed to be used with 50/50 is just going to get you more of the same. If you use 50/50 it will still be an irritant, and if you use 70/30 you run a high risk of burning out coils quickly and probably will get mediocre flavour because 70/30 is aimed at higher powered DL vaping (they vaporise more juice so generally the flavour concentration doesn't need to be so high)
I would advise you to pass on small MTL kits and look for either a 80 Watt capable Restricted DL or DL that can run coils in the 30 to 60 Watts range that are designed for use with 70/30 juice at 3mg. I had extreme difficulties with MTL when I started vaping (particularly the 70PG/30VG that was common at the time and found the combination of high PG and high mg freebase excruciating) but I found the transition to DL and 3mg vaping easy, the irritation and sore throat cleared instantly. You will plough through more juice, but the your nicotine consumption will be pretty much the same overall and the costs will be similar.
I advise looking for either a single 18650 or 3,000mah internal battery pod style kit (the internal battery versions tend to be a little smaller and lighter, but neither are huge) or a separate mod and stock coil tank, I'm totally out of date on which are the best stock coils, but something from Vaporesso or Voopoo is a safe bet. If you are wary of DL vaping - don't be, they run at a higher power level but because the power is going to a larger coil, vaporising more juice with more airflow it isn't any hotter, it just provides more vapour and flavour from 70/30 juice is unlikely to be a problem.
If you're in any doubts, look for a kit that has a lower powered, high resistance coil in the available range so if DL doesn't work for you, you can always use it in MTL style.. And don't worry about inhaling directly into your lungs and blasting it straight out again because you don't really have to - With my first DL kit I vaped it MTL initially and gradually adjusted my style of vaping until I reached somewhere in the middle of MTL and DL. I still don't vape DL 'properly' as I find a combination of the two styles suits me and gives better flavour.