Tufts actually grants PhDs in quite a few science fields. They seem to be trying to move from in-between school to R1. I know at least one department is thinking of dramatically increasing lectures sizes in order to lower the teaching load.
Dartmouth, Tufts, Emory are more R1s than LAC, in terms of everything (research expectation, teaching loads, department cultures)
Dartmouth and Tufts were included in my (non-comprehensive) list because of the lack of PhD program. And at the undergrad level, they also definitely have more of a size and feel to a SLAC than a R1. But, you're right that they're definitely closer to the R1 side the of the spectrum.