Hi Nick
It’s totally dependent on the source content in terms of style, terminology and syntactic factors, such as formatting. English to French and Spanish generally translated well in most of the popular public systems (Spanish and Portuguese normally feature at the top of the quality outputs).
If you have a glossary for your eLearning content, then either custom systems or terminology adapting engines can be created for Google AutoML, Amazon, DeepL and Microsoft MT and would give improved good output. If you don’t have a glossary, then we’ve found Google AutoML still performs well in generalized language output, but DeepL and ModernMT are worth a look and can be superior or at least equivalent in many scenarios.
MT systems can be religious turf war of opinions, so this is just mine ;)
The simple summary here is that the output, without knowing the source, is non-determinate and generally speaking, it’d be wise to conduct a test using a scoring methodology such as TER and a Human In The Loop validation to help you make a selection. There’s so much more that could be discussed from your original question, but I hope this helps!
Cheers
Stephen