Foreigners being warned against applying in large companies

I have 2 years working experience as SAP Logistics Materials Management consultant. I’m currently applying for a student visa to go to Japan and learn the language since most SAP positions I’ve seen online require business level. I’ve also been reading articles regarding working in Japan and I’ve read one in quora where contributors sort of advise foreigners against joining large companies. SAP companies tend to be mostly large ones so I’m getting concerned. My only fallback is basic knowledge acquired in school which is all over the place; HTML, PHP, CSS, javascript, basic networking, C++ and java. Should I consider going for RoR or other programming languages while studying? And is it possible for someone on student visa to get a part time programming job? The school I’ve chosen is in Nagoya since cost of living there appears to be cheaper than Tokyo.

Thank you.