The newtxmath package has something called as smallerops option which when used causes the math largeoperators (other than integrals) to render 20% less than their original font size.
My question is the following: I would like to use smallerops option (in displaymath mode) only for the "Summation" (the default summation symbol is too big). Is this possible?

\sumin displaymath mode, but not the size of other large math operators such as\prodand\coprod. Is this correct? – Mico Mar 05 '20 at 07:44\medop{\sum}(requires loadingnccmath), which does the same job. Note that if you loadmathtools, you should load nccmath first. – Bernard Mar 05 '20 at 08:41