Welcome to the forum, ncs.
I know this is not going to be exactly the answer you wanted, but it will have to suffice until others chip in.
It is a fact (I pass no judgement on this) that few reputable schools will employ beginning teachers with a purely online certificate. Most reputable schools insist on beginning teachers holding a certificate that has involved about 100 hours or more of instruction (this may be online) and at least six hours of observed teaching.
Some schools do not insist on the Trinity Cert TESOL or the Cambridge CELTA, both of which can be obtained partly through online instruction, and both of which are recognised by the British Council, but few will accept online courses with no observed teaching practice.
I know from personal experience as a trainer that some of the 100+ hours (instruction) plus 6+ hours (observed TP) are as sound as the Trinity and Cambridge courses. There are sometimes only two significant differences between them:
1. The Cambridge and Trinity validated courses are moderated by highly respected institutions. You can be 97+% sure that the particular institution whose course you are taking is sound. Other institutions claim to be validated by various self-appointed validating institutions unrecognised by any government-approved body. You may get a good course, but you may not.
2. The Cambridge and Trinity certificates are recognised and accepted by many schools and governments throughout the world. Others, even though their courses may be just as good, are not.
You'll also find that most institutions offering 100+- and 6+- hour courses are not significantly cheaper than Cambridge and Trinity courses. If some are, you have to ask yourself why. Apart from anything else, are they paying their trainers low salaries? If so, why?
As for the purely online courses with no observed teaching practice, their certificates are not worth the cost of the paper they are printed on. When I last searched, I found a couple of places offering online courses lasting only a weekend leading to an 'internationally recognised' certificate for under $200. Do you really want to work for schools (if they exist) who would employ somebody as a trained teacher on such a non-qualification?