VT, this is the charge controller that is on the back of one of the two folding panels for my 100 watt setup.
https://www.renogy.com/renogy-viewstar-20-amp-pwm-solar-charge-controller-with-lcd-display/
It is a PWM, but it has been very good at keeping my aux battery, a Optima Redtop charged up while camping.
Is it worth switching it out for one of their MPPTs?
So-called 'PWM' controllers use power electronics that vary the switch on/off as high speeds - typically tens of kHz or higher - to regulate flow. Non-PWM controllers use a liner regulator - think variable resistor - to regulate power flow. PWM is much more efficient. NEITHER have necessarily have MPPT. That particular Renogy unit does NOT have MPPT.
MPPT controllers will give you 10-30% more energy (usually closer to the higher end - especially when the modules are mounted sub-optimally to the sun). Ignore the Youtube videos about people looking at voltage when testing module outputs - it is all about the MPP -> Maximum Power Point. Power is a product of current & voltage. A module operating at max/near max voltage is NOT operating at its MPP. The difference between MPPT & Solar Charge Controllers is the MPPT algorithm will actively hunt for the MPP facilitating battery charging at higher power/energy for longer.
MSRP on that unit is $80...for a non MPPT based controller, that is hella expensive.
If your setup is working now, I'd run it until it doesn't work or you need more power/energy/need to recharge faster. Only then I would
spend money to replace a PWM only unit with an MPPT based PWM unit. If you're not taxing your system now, you may not notice a difference.
If you're in a less than optimal solar climate (NE/NW/Canada & have lots of grey days...then it would help quite a bit).
I have a number of cases where I need to re-charge quickly - ex: working the evening, only being able to deploy mobile modules for a few hours, etc. For the family use case: camping in one spot, play in another (head a short distance to a trailhead or the beach during the day where mobile modules would not work but roof modules will.) For the work case, mobility can be important during the day - setting up mobile modules doesn't work well.
I notice limitations in solar when I
work remotely in sub-optimal sun areas for more than a day (two nights) if I don't run a min of 150W - this means using comms/radios, remote cellular hotspot, cell booster, laptop via inverter, light camera gear, fridge. Laptops & cell booster can consume a surprising amount of energy. However, I deploy my modules and angle them towards the sun -> this maximizes their production. Most of the time I run 150W (3x50W) and lately have been playing with 200W (2 x 100W). A single 100W mounted flat on my roof is inadequate for my use since I like the shade. A single 100W with a mobile 50W in good sun is somewhat adequate when I like to park in the shade. Folks have way over-hyped the issue about letting batteries occasionally cycle at <100% SoC for a dew days or a site a week between full charge cycles. MOST batteries calendar out before they cycle out. I always use a charger to top off when I get home.
I wouldn't feel tied to Renogy units - and would not install it on the back of the module (since it tends to run much hotter there). A quality MPPT controller will not need the temp of the module to arrive at MPPT, but a quality battery charger will require the temp of the battery. Since you are using an Optima Battery, they have some unique charging requirements - I am not fully versed as I've never spec'd them in any of my systems (space vs cost vs energy density). I'd look for a MPPT based battery charging controller that would allow you to modify the charging profile. I'm not a fan of using the 'load' connection in any of the controllers as I find the Fuel Gauge / %full meters are never accurate. The charging current & voltage tell me all I need to know about the battery status. I like Victron + Blue Tooth, but they are expensive. I also like CTEK 250S since it controls charging while driving. Also expensive, but it allows me use high quality deep cycle VRLA batteries that have limited charging current (usually 0.3to 0.4C).
