Well...it really depends on the specific clan, battle, and war. When we are talking about local strongman vs local strongman, it's probably not too far off to assume each side only had a few hundred, or at most a couple of thousand. However, things could be quite large and lopsided. For instance, the overall engagement at Nagashino was, according to the Chronicles of Lord Nobunaga, 38,500 for the Oda and Tokugawa and 15,000 for the Takeda, with the decisive engagement at Shitaragahara 32,000 vs 12,000. And this is the lower end of pre-modern sources. And engagements after Yamazaki got stupidly large because of the wide range of resources and clans mobilized.

On the other hand... it's my experience that media often exaggerate the strength disparity to make for a better story, so I'm not sure which media you're referring to.