Cyrillic wght: 100/400/90 | WDTH: 25 | slnt: 0 | grad: -50/0/50 | opsz: 14

**wght: 100** | wdth: 25 | slnt: 0 | GRAD: -50/0/50 | opsz: 14

in Grad 50 horizontal seem to become pretty close to verticals in weight. (>see нкж) This wasn't present in wdth 100.

The rest of the comments are given for a whole range of grad -50/0/50.

LC:
з - too dark on strokes in comparison to the rest, too narrow (in comparison to аевя), needs more space on the left.
э - shifted to the left in the metrix box.
я - too much space on the left, strokes on the left side look darker.
у - shifted to the right.
б - top right part of the top curve is too light.
ий - dark on diagonal.
лд and especially шщжю - too wide.
ж - top legs looking pretty light.
ху (components from Latin) - too wide.
ф - seems narrow in comparison to the rest.
breve.cyr, breve.cyr.case - too wide.

UC:
П - slightly too wide in comparison to H.
ЦЛД - as well.
ШЩЖ - significantly too wide.
ЬЪ seem to be narrower than P.
З - needs more space on the right side.
Э - needs more space on the left side.

_________________________
**wght: 400** | wdth: 25 | slnt: 0 | GRAD: -50/0/50 | opsz: 14

LC:
б - top right part of the top curve is too light.
з - too dark on strokes, needs more space on the left.
я - too much space on the left.
вяьъы - this group is being to wide in comparison to other letters.
ж, и - slightly dark in text.
д, л - appear wide.
breve.cyr, breve.cyr.case - pretty wide and slightly dark.

UC:
П - slightly too wide in comparison to H (yet in wght 100 it's more visible).
ДЛЦШЩ - too wide.
З - too dark on the left side.
_________________________
**wght: 900** | wdth: 25 | slnt: 0 | GRAD: -50/0/50 | opsz: 14

LC:
в - horizontals too thin.
у (component from Latin) - appears very narrow, at least in Cyrillic.
з - look pretty open, I think terminals if longer and brought closer to each other might help to achieve more coherent color with other letterforms.
я - too much space on the left.
breve.cyr, breve.cyr.case - contrast seems to be pretty different between LC and UC versions. UC version could use a bit more weight on "verticals", while LC on "horizontal" part.

UC
ДЛ - too wide.
Д - the left descender seems to go further to the left than in LC д where the balance looks optimal.
ИЙ - dark in text.
З - look pretty open, I think terminals if longer and brought closer to each other might help to achieve more coherent color with other letterforms.
Ч - slightly too wide.
Я - leg is a little too dark.