One more thought, if I may... (Repeating my disclaimer that I have zero medical training)

The big tradeoff in the surgery/chemo first debate is how likely you are to get ALL the disease with surgery first; and if you don't, what condition will you be in after surgery with delayed start of the inevitable chemo.

Part of the rationale behind Total Neoadjuvant Therapy was that patients who could not tolerate chemo after surgery at least got a "full course" (arbitrary definition) of chemo as part of their treatment, improving the odds of being micro-metastasis free after surgery. (Of course the possibility of micro-/macro-metastasis while on neoadjuvant chemo is still there, so it's always a gamble.) You ( @mrajat ) being young and fit, stand a great chance of easy recovery and ability to tolerate adjuvant chemo after the surgery.

My personal thought is that 27mm x 24 mm is a pretty sizeable tumor, and the head of the pancreas is a pretty critical location in your digestive tract. IF cancer has spread anywhere else, you don't know where / how much because it's still too small to see.

My (non-medically trained) logic is that the primary tumor has billions/trillions more cells than whatever micro-metastasis has spread elsewhere; that makes it the largest possible contributor to (additional) metastasis and largest number of cells with potential to mutate.

If you start chemo first, and then later discover other mets that disqualify you from surgery, you're pretty much stuck for life with that tumor on the head of your pancreas. In my case (recurrence detected at remaining "head" of pancreas along with mets that disqualified me from surgery)... that tumor grew to block my stomach outlet and wreak havoc with the rest of my digestive tract. The visible met (actually only one visible) wasn't even detected until several weeks after the recurrence was confirmed, just as I was preparing to begin the chemo my surgeon wanted before doing a "re-Whipple" procedure.

I still have other tumors/carcinomatosis in numerous other parts of my abdomen, but they are all small and none are in critical locations. If we had gotten rid of my main tumor upon discovering it, my digestive blockage would not exist, and the remaining cancer in other areas would still be "manageable" albeit more advanced than would be the case if they had been treated earlier.

There are treatments and trials out there for what it considered "oligometastatic" disease (metastatic but limited to a small number of tumors and locations). These are bigger than micro-metastases because you obviously wouldn't be able to count them if you couldn't see them.

Long story short: IMHO, the biggest tumors in the most critical spots are likely to cause the biggest problems, and those are what I would address first.

I hope you will keep us posted regarding your final decision and eventual outcome. Good luck with it all!