stiff, tense

Uptight часто встречается.)

constrained sounds like someone tied him up or put him in handcuffs

Yes, but ''зажатый и скованный'' kind of implies that.

I also wanted to use tense but word "tense" in Russian is more like "напряжённый" which is not ''зажатый и скованный''.

Ah, i’ll delete mine then

No. leave it.

Generally speaking, your translation is still correct. It's little confusing but I've noticed that when I post a translation which is not literally what the original says (but overall makes sense and carries the correct idea), other people would start saying "oh, this is not exactly what the original says" or "this is little off" They would start posting links to Wikipedia or other sites showing the exact meaning.
But then, when I post something with exact meaning I would hear like this is too literal. And that I need to be more creative and challenge oneself for more diverse translations...
Like in this case I went and posted the exact meaning of the original. But my first choice was Uptight and tense (just like yours). Had I posted " Uptight and tens" other people would have said: "This is close but not quite the same". When you posted it no one dared.
And I 'm confused...

Russ, we all have that confusion at some point. But what's wrong with "tense"?
"unable to relax because of nervousness, anxiety, or stimulation" - this is exactly what скованный implies unless it's used as in скованный цепью/наручниками.

К слову, в случае подобных сомнений Вы можете писать бесчисленное количество вариантов в комментариях.

I didn't say there was something wrong with "tense". On the contrary, I said it could work although it does not carry the exact meaning. Even in your example, you came up to "tense" thru a list of emotional states as "unable to relax because of nervousness, anxiety, or stimulation" which may imply "зажатый и скованый" if we speak diverse.
But my point in the previous comment wasn't about this particular case but more in general. Good to know I'm not the only one who gets confused once in a while.

http://ozhegov.textologia.ru/definit/skovanniy/?q=742&n=203454
Скованный - зaтpyднённый, лишённый лёгкocти в дeйcтвияx, в пpoявлeнии чeгo-нибyдь Cкoвaннaя мыcль. Cкoвaнныe движения.
Непринуждённый - скованный =>
Relaxed - tense ¿¿🤔

A pair of synonyms in Russian (зажатый и скованный) requires a pair of synonyms in English (uptight and tense). 🤔