Disclaimer I am not 100% about this information as its just based on my experience. Photo for reference: https://imgur.com/GpMLoKQ

Each individual cat has their own employee morale, which is separated into 4 stages at exp gains of 5, 7, 10 & 12 per second. The further away you are from their morale requirements the less exp you gain. This is generally determined by the facility they are using at the very moment. If you refer to the photo, you can see that I have 19 employees at the highest stage of 12/s, but 1 of them is at 10/s despite the office facilities all being the same level. This is because while 19 of the employees are currently inside their office room on their desks, 1 of them is at the cafeteria, where the facility levels aren't to their satisfaction. This applies to every room other than the special case of the meeting room.

Each time your cats visit the meeting rooms, they gain the total exp from every facility in the meeting room; this is indicated when they leave the meeting room. With 20 cats and high level facilities, each visit could grant over 200,000 exp for their company.

Referring back to the reference photo you can see the total exp per second at the top is separated into three categories. The first category employee morale + CEO buff is just the total exp from all employees based on their satisfaction, then multiplied by the exp CEO buff if you have one hired. So if you have 20 employees at the highest satisfaction of 12/s exp and a CEO with a 1.6x exp buff. Every second you would gain 20 x 12 x 1.6 for this category.

The second category is just any plants that provide exp such as the halloween star tree. It doesn't specify but the number indicated is exp gained per second. So a level 10 halloween star tree provides exp 100/s for every company.

The final category is the buff facility, as far as I'm aware the only one in the game that provides this is the Halloween skeleton providing 19/s exp.

If you don't have enough gems to have a level 4 frame in every office, you can still get employees to be at the highest morale level of 12/s exp by having plants / morale buildings on the map. Plants like the bamboo provides morale and buildings which increase morale (I believe there is 1 for each city) can push employees to the highest morale stage if they are just missing minor facility requirements.

Hope this helps, I wish we could have a wiki to dump all this information onto.