The whole point of an HDR image is to have a wide range of luminance levels, e. g. a very bright sun spot in an otherwise modestly lit scenery, which will give you a strong directional lighting quality for your render without having to increase the strength to insane levels.
Taking a LDR image and cranking up the brightness is absolutely not the same, as the brightness of that image is cranked up across the board. It is still an image with low dynamic range afterwards - only on a much higher level. And since you increase the brightness of sky and grass areas as well, it’s no wonder these colors heavily influence your scene. Even if you could crank the brightness up so much that you have all colours blown out to pure white: Why then use a texture as environment at all? In that case you could just use a plain white environment, as even the feeble directional lighting qualities of an LDRI will be overpowered by the general brightness…:eyebrowlift2:
There are HDRIs out there that are far from being 200+ MB in size. And if those are not high res enough to also be used as a background image, well, just use your high res jpg for the camera and the low res HDR for lighting. Or render with transparent background and add a backplate image in post…
From top to bottom:
a) HDRI (strength = 2) as environment texture. Light direction is perfectly clear (shadows).
b) Same image(!) as LDRI (strength = 4). Light almost completely diffuse, strong blue tint.
c) Bit of both: LDRI for the camera, HDRI for the rest
And another example: See how much “definition” the light loses by using an LDR version (bottom) of the very same HDR file (top)?