Today there are many fonts for Tamil language, some fonts supports the sri [ஶ்ரீ] ligature and some don't, also most fonts renders the word ர், ரி, ரீ as ர், ரி, ரீ. There is no balance between these renderings. The Tamil Nadu govt in order to avoid the confusion specified that ர், ரி, ரீ should be rendered as ர், ரி, ரீ and most of the people become accustomed to this usage and moved on. As for the Word ஶ்ரீ it is a ligature of ஶ் + ரீ so some fonts renders ஶ்ரீ as ஶ்ரீ. In my opinion these are some of the best Tamil fonts.
1. Lohit Tamil Classical
This font by Red Hat renders the words properly and also looks more professional and antique. As the word classical implies the word னை will be rendered as னை. This was how the word was written before the 70's. Here is a look of how this font looks.
ஶ்ரீ கிருஷ்னர் வந்தார். அனைவரும் வணக்கம் செலுத்தினர்.
2. Noto Serif Tamil
This Font by Google is the next best font. it renders the word ர், ரி, ரீ as ர், ரி, ரீ
ஶ்ரீ கிருஷ்னர் வந்தார். அனைவரும் வணக்கம் செலுத்தினர்.
3. TAU Series Fonts
The TAU series of fonts are released by Tamil Virtual Academy[TVA]. There
is also TAU- Elango series also released by TVA don't get confused with
that series of Fonts. Of all the fonts TAU-Barathi has good font
shape and renderings. Its also like Noto serif Tamil.
ஶ்ரீ கிருஷ்னர் வந்தார். அனைவரும் வணக்கம் செலுத்தினர்.
There you have it. I believe these three fonts are enough for professional looking documents written in Tamil language.