The victron circuit diagrams always show dual pole PV Breaker/isolators between panels and MPPT, however, various sources online suggest they are not necessary, and potentially detrimental.
My space is severely limited and my panels size quite small and all individually feed their own MPPT.
Are they important?
https://www.12voltplanet.co.uk/news/isolators-for-solar-panels.html
First rule: all wires should be properly sized (proper cross section/gauge) for the maximum current you can have there.
In case there are issues, you need a way to safely disconnect the PV array even during the day. The disconnect switch must be rated at least for the PV array Isc and for the voltage you have there. Make sure that those are DC ratings (not ratings for AC) and for disconnecting under load. It's a big difference.
Also, all wires should be fused, including the PV array wires. For wires from the PV array (and PV strings), the correct type of fuse is gPV. The fuse amperage depends on Isc of the PV array. If you have more than 2 strings in parallel, you should fuse each string, too, with the same gPV type of fuses and with the amperage calculated from the string Isc/panel Isc (does not hurt if you fuse each string even for only 2 strings in parallel). These fuses are installed in fuse holders. Fuse holders should not be used as a disconnector switch (do not open the fuse holders under load/when there is a current).
Now, if you have one-two 100W/12V (12V nominal) panels in a string or something like that - so low voltage and low currents - (and no panels/strings in parallel), the potential danger is much lower so you might be fine with a direct connection to the MPPT charger. Just make sure that the PV wires are properly sized for the maximum current you can have there, like I wrote in the beginning.
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A related comment:
No matter how small system you have, all positive wires between any equipment (MPPT, inverter, etc.) and the battery should be fused.
The 12V planet article you linked to states "If you need to work on the solar part of your 12 volt system you would probably be advised to isolate your battery from the solar controller, and this can be achieved simply by removing the fuse in the positive cable between the solar controller and the battery."
However, the advice I normally see is that you should isolate the panels from the controller before you isolate the controller from the battery. This is to avoid problems with controllers that may end up having a higher voltage leaking to the output or getting the auto sensed 12 or 24V battery setting. On my boat my panel voltage is typically in the range of 70 to 80V and I would not be happy isolating the panels from the controller by breaking the MC4 connectors or disconnecting the wire from the controller with a blanket over the panels so I have double pole DC rated MCBs.
