Hi,
im wanted to ask this because im now reading about port vlans and bridge vlans and i still not fully understand how bridge vlans work or how to properly configure it. What i have right now i belive is called port vlans.
Im using a RB750GR3 for a office/store with 5 networks, dual wans and L2TP VPN server with ipsec.

There are 5 bridges, one for each network:

Bridge-Admin -> This is were all the admin stuff is connected to diferent servers, some pcs, access points, managed switch... etc
Bridge-Sales -> The main big network were all user computers are pluged in, this is also the network the VPNs clients in offsite locations also running mikrotik routers connects to.
Bridge-Employees -> Internet-only network, mainly for private wifi.
Bridge-Clients -> A hotspot for clients is running here.
Bridge-Cameras -> A Security ip cameras network

Vlan Interfaces:
vlan1-Sales (ID 100)
vlan2-Employees (ID 200)
vlan3-Clients (ID 300)
vlan4-Cameras (ID 400)
All vlan interfaces are attached to "Bridge-Admin" interface.

Bridge ports:
ether-3 and ether-4 on "Bridge-Admin"
ether-5 on "Bridge-Sales"
vlan1-Sales on "Bridge-Sales"
vlan2-Employees on "Bridge-Employees"
vlan3-Clients on "Bridge-Clients"
vlan4-Cameras on "Bridge-Cameras"

(ether1 and 2 are wans)

Switchs:
1) 16-Port gigabit unmanaged switch on ether-3 (admin network)
2) 24-Port gigabit unmanaged switch on ether-5 (sales network)
3) 26-Port 10/100 managed switch on ether-4 (admin network) this is a old one, a 3com 2226 plus but it works.

So ether-4 is acting as a vlan trunk for the managed switch, this switch has untagged ports for all vlans, mainly intended for the ip cameras, low bandwidth devices of the sales network and wired devices of the employees and clients networks,

All my EAP access points are connected to the unmanaged 16 port switch on the admin network on ether3, and they create the wifis attached to the employees and clients vlans.

This configuration is running fine for me and has been for some time, so im wondering if i should investigate into bridge vlans for this application.

I try to simplify where possible.
I would use a single bridge and use the VLANS for any required separation.

The best advice I could give is read through this thread.
viewtopic.php?f=13&t=143620

i see, i think i understand, one bridge with all vlans attached to it, have the address, interface list, dhcp server, etc running directly on the vlan.

Vlan Interfaces:
vlan1-Sales (ID 100)
vlan2-Employees (ID 200)
vlan3-Clients (ID 300)
vlan4-Cameras (ID 400)
All attached to "Bridge1-Admin"

Bridge:
-Bridge1-Admin (vlan filtering yes, pvid=1)

Bridge ports:
-ether3 pvid=1
-ether4 pvid=1
-ether5 pvid=100

Bridge vlan:
-interface=Bridge1-Admin, vlan id=1, untagged=Bridge1-Admin,ether3,ether4
-interface=Bridge1-Admin, vlan id=100, untagged=ether5, tagged=ether4, vlan1-Sales
-interface=Bridge1-Admin, vlan id=200, tagged=ether4, vlan2-Employees
-interface=Bridge1-Admin, vlan id=300, tagged=ether4, vlan3-Clients
-interface=Bridge1-Admin, vlan id=400, tagged=ether4, vlan4-Cameras

I wish i knew about this before configuring the offsites mikrotik routers, im not using vlans there, but im using diferent bridges for diferent networks, i could do that with just one bridge and vlans :/

I would not use pvid=1 on anything but the default setup/setting for the bridge itself.
If you need an admin/mgnment lan, use vlan99 or something other than 1

(this is covered in the link from above and from my personal experience lol)

Ill need to check if the managed switch has no issues with not having a ID 1 first, it is very old.

Now that ive been reading that and the mikrotik page about potential issues of bridging vlans like im doing i wonder if this is the reason of why im having so many issues with the ip cams, some of them stops responding randomly after a few days, i cant ip or mac ping them, and its not the cameras because i dont have to reboot them, this is fixed by just un-plug the ethernet cable and plug-in again.

Note that the bridge itself keeps the pvid1 setting by default.
I have found that keeping the default pvid1 setting in old switches creates no issues for me but once up and running you can experiment.
The key is that as along as you can reach the switch to make changes thats all that I need anyway.