There are tons of clone mech mods out there, and they don't seem to have a higher failure rate. Some of them are decent and hard to tell from authentics, others are terribly machined and awful. Read the reviews of any clone you are thinking of buying, you can often learn a lot from people who have used the one you're thinking of buying. I have a few clone mechs, that I bought before I decided that it's only authentics for me. Some of my tubes don't have venting holes but I have never had a battery vent....way more important a safety feature than holes is your head. If you feel your tube or button getting hot, put it down and let it cool. Heat will be your first warning of any problems. I am definitely not saying that lack of vent holes is 'safe', and I would always suggest that especially if you're new to tubes, that you use a mod with vent holes. I just wouldn't be paranoid about it. If you're planning to build 'stupid low', then for sure you want the 'safest' tube mod you can get. There are a lot of 'entry level' tube mods these days, with delrin liners and button venting. If your mod is designed to vent through the hole, I would suggest using your battery 'upside down'...with the positive pole to the button. As with anything, risk is part of deal, being vigilant is your best defense. Tube mods are incredibly simple, and while there are some really crappy clones out there, from what I have seen, it's usually the aesthetics of the mod that is really crappy, more than the actual design. In theory a clone has the exact same design as an authentic and therefore is as 'safe' or 'unsafe' as the authentic....provided it's a 'quality clone'. I have bought a few really nice authentics from local shops cheap, because few people seem to be buying tubes from shops these days. I got a $160 tube mod for $10 last year, because the shop owner 'just wanted it out of his shop after having it sit there with a $200 price tag for two years. It's one of my favorites.Good luck and be safe! Always use good, appropriate batteries in good shape...with a mech there is very little room for error.
To the OP:
Read the above post, then read it again. It is probably the best answer to your question.
I too have used many clone mechs in the $10-20 range from Fast Tech and 3fvape and they have all pretty much performed as expected, which is very well...and I still have my nose and all of my fingers.
And you certainly do not need to spend 200 bucks on an authentic mod when you can get a great mech tube for pennies on the dollar.
Having said that, you can also get some affordable authentic mech mods from some of the well known manufacturers like Geekvape and Wismec, among others. Not sure of current availability.
The only thing I would add to stormjib's post above is that if you install your battery with the negative pole UP (towards your atomizer), make sure your battery wrap is 100% free of any nicks or tears. If the outer case of your battery shorts to the tube, you will have a direct short when you fire the mod and the battery may run away. The best way to prevent a short like this is to buy a mech with a plastic liner that will prevent any short. Just to be clear, however: you should NEVER use a battery with a torn wrap, regardless of orientation, in any mod.