The source of protein itself is not a main variable in terms of potency, what is likely to affect the 'hardcoreness' of it is the exactly how it is processed, concentration, partner ingredients, any heat applied, processing time and your hair type.

You can make the DIY gelatin (yes hydrolysed) treatment as strong or as weak as you like, or you can buy some Colorful neutral protein filler and again make that as strong or as weak as you like. Or you can purchase a everyday type protein conditioner and try leaving that overnight.

Possible penetration enhancers .... I tried layering a drying type protein treatment under a light conditioner containing these ingredients then shower capping instead of leaving to dry. Did seem to stop the straw effect.
"We found that using Aloe Vera along with Behentrimonium Methosulfate creates a more effective protein treatment. Aloe Vera paired with Behentrimonium Methosulfate act as a carrier for the proteins allowing them to further penetrate the hair shaft to minimize protein build-up."
Products - Komaza Care

Cassia and henna are two different plants, the 'neutral henna' thing is misleading cassia is actually the same thing as senna. AFAIK cassia does not permanently bind to hair, it is temporary. I think it's more of a film former but not certain of that.
Henna for Hair : Cassia Obovata
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect