Might be the original Chinese school was a bit different from what we know in Japan now .
I think that one can be quite sure about this, and probably any school of Buddhism...
I do not know how much of original tien-tai survived within Chinese buddhism. But in Japan beside heavy tantra influence they use almost same teaching system for different parts, like period division of Budhha's teaching etc. Is in Chinese school so much tantric practice like in Japan?
What little I know of Chinese Tiantai does not really have any tantra at all.
It uses mainly earlier texts, especially those by Master Zhiyi (Zhizhe) himself,
including the various sutra commentaries, the doxography systems (panjiao),
and the four meditation texts (Mohe Zhiguan, Xiao Zhiguan, Shi Chanboluomi, Liu Miaomen).
A few Chinese Tiantai teachers of late have connections with Japan,
but I don't know the details.
But, perhaps the most important point, is to not think of the Chinese "schools"
as distinct and separate "schools" at all. From the Japanese perspective,
some comment (criticize) the Chinese schools as being "syncretic", somehow
mixing or combining originally pure schools together. But really, when one
looks at the situation in China throughout most of it's history, these are not
distinct schools, but just groups that focus on particular aspects. When it comes
to the practice of a given person, one uses the thought and system of a given
group with respect to a particular practice, and that of another group for
other practices. Originally, they are almost all Mahayana systems anyhow,
and a large number of Mahayana sutras and sastras contain these full range
of elements already. eg. purification of a buddha-field in a Prajnaparamita sutra
- so, is that "Pure Land" or "San Lun", or what? - answer: wrong question!