Cyrillic wght: 100-900 | wdth: 100 | slnt: 0 | GRAD: -50 - +50 | opsz: 14

Here are my observations for grad -50 and 50
I already posted about grad 0 [here](https://github.com/TypeNetwork/Roboto-Flex/issues/184) Looking at whole range together: Grads -50 and 50 are consistent with grad 0, however some of the issues become more pronounced.
__________________________________________
wght: 100 | wdth: 100 | slnt: 0 | opsz: 14

Grad -50:
1. И diagonal is too light (see Ии together). This is still slightly present in Grad 0.
2. Л feels generous in width

Grad +50:
1. breve.cyr and breve.cyr.case - could have a little more weight on the 'vertical' parts, which would support both their presence and modulation more coherent with letterforms.

__________________________________________
wght: 400 | wdth: 100 | slnt: 0 | opsz: 14

Grad -50,0,50:
1. breve.cyr and breve.cyr.case seem dark in comparison to letterforms, I would also recommend more contrast for them.
2. ж,Ж are slightly dark in Grad -50, same was reported for Grad 0. This becomes most present in Grad 50, same for dark и.

Grad 50:
1. л - the leg (left stroke) feels a little dark in Grad 50.

__________________________________
wght: 900 | wdth: 100 | slnt: 0 | opsz: 14

Grad -50,0,50:
1. в is too thin on horizontals
2. У is too thin on its top part
3. breve.cyr and breve.cyr.case are too thin

Grad -50:
1. Д, but especially Л seem light/bright in text.

Grad 50:
Cyrillic issues described below are related to the features which come from Latin:
- dark diagonals (esp. in UC)
- weight relation between verticals and horizontals: they seem more differentiated in UC than in LC.
As a result Latin M is dark while H and O is much less. O and o observed together give slightly different feeling of modulation, O is lighter on horizontals. Cyrillic features described below are partly a consequence to this, but perhaps these could be made slightly more subtle?

1. Л appears light/bright, esp. in title case setting. Д has same feature but to smaller extent. LC л and д don't have that.
2. Ии appear dark in text.
3. Same as Ж which could be noticed in Grad 0, but is more present in Grad 50.