Whelp. Throw my hat into the ring:
Version: 0.866r LIVE (Gear, scroll all the way down)

Cassandra: lvl 226, earnings: 35.79Sx/s, levelup: 440.19Sp
Laura: lvl 226, earnings: 35.79Sx/s, levelup: 564.18Sp
Anika: lvl 226, earnings: 35.79Sx/s, levelup: 688.19Sp

"level" in terms of texting means nothing. At least on my version it doesn't seem to have *any* impact on how much money the girls make or how much upgrades cost. All it does is unlock photos. Even finishing a girl's entire story makes no difference.

Decorations:
Computer (I think?): lvl 2: +200 Prestige
Toy Box (I think?): lvl 4: +800 Prestige, -4% Level Cost Reduction
Heavy Bag (type you punch): lvl 6: +900 Prestige, +7.00x Tapping Power
Coffee (Beer): lvl 13: +2.6k Prestige, +780.00s Booster Time
Pot: lvl 8: _1.6k Prestige, +1.60x Company Multiplier
Orange Chair: Lvl 6, +1.2k PRestige, -12.00% Base Cost
Fern: lvl 10, +1.0k Prestige, -10.00s Private Show Spawn Time

Note: It's possible different people unlocked different decorations that do other things, maybe add multipliers to certain desks, and/or multiplier based on number of unlocked photos for a girl or somesuch?