If Nepal was unified in 14th century instead 18th century drastically changes, for one, there would be a Stable State in the Subcontinent, one that is united by Language and Culture and seems to have much more robust foundations than any other Subcontinental States, Nepal would be perhaps bit bigger than in OTL, with Sikkim, Parts of Uttar Pradesh and Uttarakhand being attached to it, as such it would be a pretty big state, with great defensive geography and ability to raid the fertile plains of Indo Gangetic region and hide back in the Mountains, like how Afghans did, but on a bigger scale, raiding regions like Bengal, Punjab, Awadh, etc would have become an easy source of revenue for Nepal, but just like how Afghans under Durrani started building an empire, so would Nepal, and unlike Afghanistan, which is in middle of trade routes and surrounded by enemies, Nepal is safely tucked away in the Himalayas
With Timur Sacking Delhi, North India would again be in Chaos, allowing Nepal to swoop in and Conquer large parts of Indian Subcontinent, Such as parts Bengal, Bihar, Uttar Pradesh, Punjab, Bengal would be a very important province at it would give Nepal access to the sea, which would be instrumental for Nepal in order for it to be Independent in exports, Inevitable when another Pashtun Muslim power arises, there would be clashes with this new Nepali Empire, Both will win and lose some, but seeing how Afghans in OTL lost to an Ethnic Group was united under Cultural and Religious unity, The Sikhs, Nepal would have much easier time as they would have more time being established, they could also appeal to non Nepalis as fellow Hindu liberators against Islamic conquest, which will rile up support but create opposition as well
Let's say before age of Exploration, Nepal is empire, with Territories in OTL Nepal, Uttarakhand, North East, Bengal, Bihar, Uttar Pradesh, Punjab, Kashmir and Tibet, Would they would call their country would be Nepali, though a sizable portion will call it Bharat as it was what Hindus called the land, and Language would be Nepali, In Devanagari Script, it would be called Nepali, but would inevitably have loan words from other Indian Languages like Bengali, Punjabi etc