The make up of Russians squads is varied depending on the branch of service: Motorized, Mechanized, VDV, VDV Mechanized, OMON, Interior troops, Border Guards or Marines. Also whether they are front-line, second line or third line/militia.
Nearly all frontline troops are issued the AK-74. VDV (paratroopers) are generally issued the folding stock variants. AKSU are rare for frontline units but can be found amongst OMON, vehicle crew, special forces and police units. (There is no such unit as Spetznatz, it is more a coverall term for special forces. If you want to do a more realistic Russian Special Forces loadout, look up Alfa Gruppe, Vympel, OMON or VDV Recon. These guys are badass. For instance following a kidnapping of Russian dignataries in Lebanon in the 80's, Alfa Gruppe rounded up the kidnappers friends and family members and severed there limbs until the kidnappers realeased the hostages. Which they did.)
Anyway, back on topic. The SVD is used as Marksman rifle and Sniper. It was originally designed for Russian Squads to stretch their fire-power beyond 600m. In motorized/mechanized platoons, one squad will be issued a single SVD. VDV will generally have one per squad. I dont have any info for the marines, but other specialist units will have designated sniper teams that will use them. The russians have access to a large number of varied sniper rifles. In the Beslan School Crisis there are pictures of Alfa Gruppe snipers using the L96!
Frontline units, VDV and specialist units will be the best equipped. Militia and thrid line troops will still be issued with far older gear. Ak47s, AKMs and RPKs are very common amongst these units.
Hope this helps.
Nell