  We study avatars of T-duality within Sen's formalism for self-dual field
strengths in various dimensions. This formalism is shown to naturally
accommodate the T-duality relation between Type IIA/IIB theories when
compactified on a circle without the need for imposing the self-duality
constraint by hand, as is usually done. We also continue our study of this
formalism on two-dimensional target spacetimes and initiate its study as a
worldsheet theory. In particular, we show that Sen's action provides a natural
worldsheet-based understanding of twisted and asymmetrically twisted strings.
Finally, we show that the $\mathrm{T}\bar{\mathrm{T}}$-deformed theory of left-
and right-chiral bosons described in Sen's formalism possesses a scaling limit
that is related via field-theoretic T-duality to a recently studied integrable
deformation of quantum mechanics.
